Keir Starmer's former boss and mentor has blasted the Government's plan to scrap thousands of jury trials a year as a 'betrayal of Labour traditions and values'.

Geoffrey Robertson KC said legislation that will slash the right to trial by jury risked being a 'cure worse than the disease'.

The measures – which Labour claims are necessary to slash the record Crown court backlog of 80,000 cases - have come under widespread attack from MPs and the legal profession.

Now the Prime Minister's former colleague Mr Robertson has condemned the plans and suggested they will even make the backlog worse.

'Given its record of support for progressive causes, for free speech and peaceful political protests, the Bill does seem a betrayal of Labour traditions and values,' Mr Robertson wrote in a paper for the Bar Council.

'MPs who vote in favour will be on the wrong side of their party's own history.'

He added: 'It might be thought that Labour of all parties would be careful about messing with a system particularly venerated by most of its members and supporters.'

The Courts and Tribunals Bill will apply retrospectively, meaning that defendants whose cases are already in the backlog and are currently entitled to trial by jury may instead be tried by a judge sitting alone.

Mr Robertson said: 'Applying these changes retrospectively amounts to a fundamental injustice, undermining legal certainty and the long-standing principle that individuals should be tried according to the rules in place at the time of the alleged offence.'

He suggested the measures would lead to voters punishing Labour in the polling booths.

'This is a Labour initiative, and unless it is withdrawn, the government will face rejection by people whose support for jury trial may be demonstrated at the ballot box,' the KC wrote.

Mr Robertson went on to say Labour's measures will increase pre-trial hearings – therefore taking up court time that could otherwise be spent on trials.

Judges who hear cases without a jury will also be required to publish a written judgment, taking up time they could otherwise spend overseeing jury trials, he added.

'From this draft legislation it can be seen how this ill-conceived plan to demolish jury trial may in fact cause more delays than it could ever serve to reduce,' Mr Robertson wrote, adding that the moves would 'impede the work of reducing the backlog'.

The barrister added: 'Labour is taking an axe to a piece of English heritage, one part of a criminal justice system which unlike the others, is actually trusted by most people.'

After Sir Keir completed his law degree at Leeds University and a postgraduate law degree at Oxford University in 1986 he was hired by Mr Robertson.

Mr Robertson wrote an article headlined 'Keir Starmer was once my apprentice – and this is how I think he might fare as prime minister' in the Guardian newspaper as Labour came to power in 2024.

He wrote: 'After university he applied to join my chambers. Keir interviewed badly, lacking both confidence and dress sense. But I needed a junior, and so we took Keir on.'

Sir Keir went on to be a founding member of Doughty Street Chambers, where Mr Robertson was head of chambers.

Bar Council chairman Kirsty Brimelow KC said: 'I hope many MPs will read this profound and professional analysis and stop the jury-wrecking parts of the Bill in its tracks.'

The Bill is being overseen by Lord Chancellor and Justice Secretary David Lammy. 

An MoJ source said: 'The criminal justice system we inherited is on the brink of collapse.

'Years of inaction by the Tories have created a system that is no longer fit for purpose, where justice delayed has become justice denied.

'Only a combination of investment, modernisation and reform can turn the tide on the backlog before the end of the Parliament.

'The alternative to this package is the Tory status quo: continued drift, collapsed trials, and victims walking away from the system entirely.

'This Labour government chooses a system that works for victims, providing brave survivors with the 21st-century justice they deserve.'