For most of his working life, John Flavin championed health and safety in the workplace – so it's no exaggeration to say he probably saved scores of lives.

As a president of the Union of Construction, Allied Trades and Technicians (UCATT) in the 1990s, and as an on-site campaigner in the 1970s, he helped revolutionise the way workers were protected on building sites.

He then took that experience into the boardroom, rising to become a group executive at construction giant Laing O'Rourke.

'When he began campaigning in the 1970s, workers weren't even required to wear hard hats on building sites,' says his proud daughter Anita, 55.

'He made construction a much safer industry and he always tried to make progress through negotiation and not strike action. He was a wonderful man.'

So it was a particularly bitter pill for his family to swallow when, in August 2021 at the age of 77, John was diagnosed with lung cancer caused by exposure to asbestos at a time when people cared less about safety than he did. 'He was coughing up blood,' says Anita. 'But he was so fit, exercising every day and even running marathons that he couldn't believe it was anything serious – and he'd never smoked. He ended up in A&E and they found a huge tumour in his right lung. At first, they said there was nothing they could do for him. Then, because he was so fit, they decided to remove part of the lung to get the cancer.'

John, who lived with his wife Maureen, 87, in west London, survived the operation but died the following year after a brave fight, making him one of an estimated 2,500 a year who die from asbestos-related lung cancer.

According to figures released by the Health and Safety Executive (HSE), another 2,500 die each year from mesothelioma, an always fatal cancer of the mesothelium, the membrane surrounding the outside of the lungs and abdomen linked to asbestos exposure. These two cohorts of 2,500 each are referred to by the HSE as the 1:1 ratio.

However, experts now question this ratio – and warn that the number of asbestos-related lung cancer cases is vastly underestimated. If they're right, instead of 5,000 deaths a year, Britain's biggest industrial killer could be causing 22,500 – and new research shared exclusively with the Daily Mail appears to bear this out.

Our campaign, Asbestos: Britain's Hidden Killer, has been calling on the Government to introduce a 40-year phased removal of asbestos from all public buildings, starting with schools and hospitals. The current policy is to leave it where it is, as long as it isn't visibly deteriorating.

We say this research makes the call for a change in policy even more urgent. Traditionally, white asbestos – the one most commonly found in buildings, including more than 80 per cent of schools and 90 per cent of hospitals – has been regarded as less deadly than blue and brown asbestos as a cause of mesothelioma.

But the research, conducted by Daniel Murphy, Professor of Lung Cancer and Mesothelioma at the University of Glasgow, suggests white asbestos is much more likely than blue or brown to cause lung cancer. And because tumours caused by asbestos look the same in the lung as those caused by smoking, they are being attributed to the latter.

At the microscopic level, blue and brown asbestos fibres are sharp and straight. Over decades they work their way out of the lung and into the surrounding mesothelium's pleura – a thin two-layered membrane covering the outside of the lungs and lining the chest cavity. This causes mesothelioma. Once a person has been diagnosed, they usually die within 12 to 18 months.

White asbestos fibres are curled, so get trapped inside the lung. This means they have been regarded as lower risk for mesothelioma, which occurs outside. Professor Murphy's research involved bypassing the lung and injecting white asbestos into mice pleura to see whether it was, indeed, less dangerous than blue and brown. It wasn't.

'White asbestos reduced the lifespan of the mice just as much as the blue and brown,' he says. 'This leads to the question of what it is doing while it is trapped inside the lung. It will be causing the same kind of chronic inflammation inside the lung as the blue and brown are causing in the pleura outside it. And this is going to accelerate disease onset and lung cancer.'

Professor Murphy's work is ongoing but he now believes the overall death toll of mesothelioma, lung cancer and asbestosis (a non-cancerous hardening of the lungs) is not the 5,000 a year HSE figure. The watchdog stands by its data, but he believes it is likely to be between 9,000 and 22,500. The range is so wide because there is no absolute figure for the numbers of lung cancers caused by blue, brown and white asbestos. However, the HSE's own figures say white asbestos is almost nine times as likely to cause lung cancer than mesothelioma. 'This range is my interpretation combining the epidemiology with our observation in mice and the HSE's reported figures,' says Professor Murphy.

In response to the claims, a HSE spokesperson said: 

'Every death caused by asbestos is a tragedy which is why we are working at pace and scale to make sure the risks it still poses are fully understood and mitigated.

Our assessment that asbestos causes roughly equal numbers of lung cancer and mesothelioma deaths is based on a substantial body of evidence, including the most recent work by leading independent researchers.

Last year, HSE brought together the widest range of asbestos experts and stakeholders we have convened to identify the research priorities that will underpin better decision-making for years to come.'

But when patients such as John are diagnosed with lung cancer – and report that they smoked – their cancer is usually put down to smoking. Because John never smoked, further investigations established that his exposure to huge amounts of asbestos when he was young was the cause.

In a statement taken before he died, John described transporting large amounts of raw asbestos used for insulation for a variety of employers, being surrounded by clouds of asbestos dust and even mixing asbestos powder four or five times a day in large drums from the age of 15.

'I was not provided with any protection during my employment…nor was I given any warnings or advice about the dangers of asbestos, or the measures I should take to avoid inhaling dust,' he said.

With the support of lawyers Irwin Mitchell, he received compensation from Sir Robert McAlpine Ltd, Raven Mount Services Ltd, and Installations (Ealing) Ltd though none admitted liability. But others whose lung cancers were assumed to have been caused by smoking won't have been so lucky.

Hari Bains, 68, the father of Harminder Bains of Leigh Day, arguably Britain's most prominent asbestos lawyer, died from mesothelioma in 2000 after years of working at the naval dockyard in Chatham, Kent. He received compensation but the latest research has given Bains pause for thought.

'When I was growing up, the fathers of so many of my friends who worked with my father at the dockyard died from lung cancer,' she says. 'I now wonder how many of those had been caused by asbestos and how many never received the compensation they were due.'

George Connor, 83, has lung cancer after being exposed to asbestos. When I interview him, he sounds exhausted. He and his wife Greta, 80, are coping with his illness at their home in Trimdon, County Durham. They have four grandchildren and seven great-grandchildren.

George was a bus driver for most of his life but at 15 worked at William H. Brown Shipbuilders in Hartlepool. He was an apprentice plater, whose job was to cut and shape the heavy steel plates used to build the frames of ships.

'But there was so much work on at the time that we had to do lots of other jobs, too,' he says. 'We used to lag boilers and pipes with asbestos that we mixed into a paste in big barrels, often with our hands. There was no protective clothing. We used to wrap scarves around our faces while we'd be climbing inside the boilers and the ships' funnels, lining them with asbestos and wire wool. There was asbestos dust everywhere and we just breathed it in.'

A year ago, George had a stomach bleed. Further investigations discovered lung cancer. Doctors found pleural plaques, showing he had suffered asbestos exposure but a claim for Industrial Injuries Disablement Benefit (IIDB) was rejected by the Department for Work and Pensions. His lawyers, Thompsons, are appealing on the basis that his work was tantamount to 'asbestos insulation work', which should qualify.

'George had smoked but he gave up at least 40 years ago,' says Greta. 'We believe that if smoking had caused his cancer, it would have shown up long ago. They gave him a 30 per cent chance of living a year and that time is up now. We're hoping George has much longer but the impact on our lives has been devastating.'

The failure to recognise that so many lung cancer deaths were likely caused by asbestos is resulting in hardship for victims during their last agonising days. While they are eligible for some benefits, IIDB is often denied them. And, for complex legal reasons, any damages they are able to claim can be much lower than for mesothelioma victims.

According to Professor Jukka Takala, former President of the International Commission on Occupational Health and one of the world's most renowned experts on asbestos-related diseases, the UK is becoming isolated in minimising the role of asbestos in lung cancer.

'Many medical doctors still believe that in the UK you are different – and they have no evidence for that,' says Professor Takala. 'In the UK, the thinking is, "No, we don't have such a high proportion of lung cancer compared with mesothelioma". But the evidence is clear and those who study this all over the world know it is.'

At a recent asbestos conference in Birmingham, Charles Pickles, founder of campaign group Airtight On Asbestos, invited industry experts and academics to write down what they believed to be the true ratio of mesothelioma to lung cancers. The consensus was that it should be around 1:8.

'British asbestos deaths are massively underestimated by the HSE,' says Charles. 'International research, and the HSE's own, certainly does not support the 1:1 ratio. There may be some scientific debate over where exactly that ratio should be, with academic papers suggesting a ratio between 1:5 and 1:9. But definitely not 1:1.'

Airtight On Asbestos has now launched a Parliamentary petition demanding that the Government review the 1:1 ratio.

Meanwhile, John Flavin's daughter says he would be disappointed over the apparently wilful decision to ignore the role asbestos has played in so many deaths.

'After all the years and effort my dad put in to make life better for people at work, he would be turning in his grave if he knew that the deaths of thousands exposed to asbestos are being ignored,' she says. 'These should be recognised as industrial deaths and the victims should get the compensation and support they deserve.'

Sign the Airtight On Asbestos petition at: petition.parliament.uk/petitions/767813