Sadiq Khan is a 'bad person' and a 'horrible representative' for Britain, Donald Trump has said as he intensified his ongoing war of words with the Mayor of London.

Speaking to reporters in the White House as he met with NATO Secretary-General Mark Rutte, Mr Trump blasted Mr Khan as he criticised what he saw as the UK's failure to tackle issues with immigration and crime.

'You have a terrible Mayor of London, by the way. I don't want to cause any problems but your Mayor of London is grossly incompetent, a bad person and a horrible representative for your country,' he said.

'The Mayor of London is a horror show. You have a crime problem, an immigration problem - the immigration helps cause the crime, by the way.'

It's the latest in a series of barbs traded by the pair, and comes just days after Mr Khan appeared to link Mr Trump's electoral success with a rise in online threats targeting him.

Speaking to Italian newspaper La Repubblica earlier this week, he claimed threats against him rose '2,000 per cent' after Mr Trump was elected for the first time in 2016, and have risen '100 per cent' during his second term.

'I am still under police protection. That shouldn’t be the price of being mayor,' he said.

Asked why Trump has such a problem with him, the Mayor added: 'Because we are a progressive, liberal, diverse, multicultural and highly successful city. London is the antithesis of those who believe in a single ethnicity, a single religion, a single culture. 

'That’s why Trump and MAGA attack us. But China and Russia also spread disinformation, helped by the complacency of big tech. Yet we Londoners are proud to live in a city that is increasingly cleaner, more welcoming, prosperous and safe.'

The Mayor of London was contacted for comment. 

Mr Trump and Mr Khan have verbally sparred for years, their feud having ignited in 2015 as the Apprentice star ran for his first term on a platform of banning Muslims from the United States.

But the arguments have intensified in recent months after the President claimed, without evidence, that London wanted 'to go to Sharia law' under the Mayor in a speech to the United Nations.

Delivering a strong anti-immigration riposte at the General Assembly last September, he said: 'I look at London where you have a terrible mayor, a terrible, terrible mayor and it's been so changed, so changed. 

'Now they want to go to Sharia law, but you're in a different country, you can't do that.'

Responding, the Labour mayor said Trump had 'shown he is racist, he is sexist, he is misogynistic and he is Islamophobic'.

The war of words reached boiling point last December when Mr Trump told Politico that Mr Khan was a 'horrible, vicious, disgusting mayor' and that Britain was 'allowing people just to come in'.

In a non-sequitur while discussing European elections, he added: 'Your mayor of London. He’s a disaster. He’s a disaster. He’s got a totally different ideology of what he’s supposed to have. And he gets elected because so many people have come in.

'They vote for him now because you know, it’s like ... it’s uh, one of those things. But I hate what’s happened to London, and I hate what’s happened to Paris. I hate when I see it.'

Mr Khan, firing back, said Americans were 'flocking' to London, adding: 'I literally have no idea why President Trump is so obsessed with this mayor of London.'

He later told the Big Issue: 'It’s like I’m living rent-free inside this guy’s head for 10 years now.'

Downing Street was pulled into the row after outgoing Prime Minister Keir Starmer was accused of failing to stand up for Mr Khan following the remarks.

A spokesman for the PM said at the time that Mr Starmer had strong relationships with both leaders.

Trump's feud with the Mayor of London comes as the capital was named as one of the first cities that will be examined under a national inquiry into grooming gangs.

Mr Khan has been criticised in the past by London Assembly Conservatives leader Susan Hall for 'taking the mickey' out of victims of child sex exploitation after he said there was 'no indication of grooming gangs' in the city.

Mr Trump also used his meeting with Mr Rutte on Wednesday to offer up his first comments on PM-in-waiting Andy Burnham, telling reporters: 'I hear he's extremely liberal, extremely, so that means he probably won't open up the North Sea.'

He then called for Britain to offer up its North Sea oil reserves, claiming the world's energy juggernauts would pay 'billions of dollars' to access its riches.

'You have the greatest oil field in the world, one of them, it's called the North Sea oil. All you have to do is bid it out to Exxon, Chevron, Shell, British Petroleum - they are begging to go there and pay billions of dollars,' he said.

'And because the Left is so crazy they don't want the money and the country is going to go bankrupt. Most countries don't have that, they don't have the North Sea oil.'