Mr Trump had dubbed Sadiq Khan a 'disaster' on Twitter over the weekend and called him a 'national disgrace who is destroying the city of London'.
Tory leadership hopeful, Foreign Secretary Jeremy Hunt, said he agreed with the President '150 per cent' while saying he would have used 'different words'.
The President's comments accompanied a retweet of a post by Katie Hopkins which called the capital 'Stab-City' and 'Khan's Londonistan' alongside two screenshots of BBC News articles detailing recent outbreaks of violent crime.
London Mayor Sadiq Khan alleged this morning that Donald Trump was become an inspirational figure for racists the world over
Speaking in central London today Said Khan said Mr Trump should explain his tweets saying it was 'remarkable' that the President had been 'amplifying a racist tweet'.
He went on: 'That's one of my concerns about Donald Trump - he's now seen as a poster boy for racists around the world, whether you're a racist in this country, whether you're a racist in Hungary, a racist in Italy, or a racist in France.
'He's now a poster boy for the far-right movement and that should cause us huge concern.'
The London Mayor went on: 'It's for Donald Trump to answer the question why he's obsessed with me, it's for Donald Trump to answer the question why he amplifies the tweets of far-right activists, why he amplifies racist tweets.
'I'm quite clear, there are many cities across this country facing a huge issue of the increase in violent crime, they've been doing so since 2014.
'There are many good leaders in America facing massive increases in violent crime, they have my support to make sure we learn lessons from each other and that we work together to grapple the issue of violent crime taking place in many cities across the Western world.'
The President continued his long-running feud with the London mayor this weekend
Mr Khan responded after the President retweeted content posted by Katie Hopkins about recent crimes in the capital city
US President Donald Trump said Sadia Khan was a 'disaster' and a 'national disgrace'
At a Tory leadership event today, Jeremy Hunt said he agrees '150%' with US President Donald Trump's assessment of London Mayor Sadiq Khan's record on tackling knife crime.
Foreign Secretary Mr Hunt intervened in the row during a Tory leadership hustings in Westminster, saying that the US president 'has his own style' and he 'would not use those words myself'.
'But the sentiment is enormous disappointment that we have a Mayor of London who has completely failed to tackle knife crime and has spent more time on politics than the actual business of making Londoners safer and in that I 150% agree with the president.'
The capital's murder toll for 2019 hit 60 today after a man in his 40s was stabbed to death this morning.
He was the fourth person to be killed in London this weekend alone, after one teenager was shot dead and another was stabbed to death on Saturday, following the fatal knifing of another man in Tower Hamlets on Friday.
This morning's victim was attacked in Stratford, east London, just one day after a mob of 100 youths pelted police with bottles as they investigated a robbery at the nearby Westfield shopping centre.
He said: 'I think President Trump should stick to domestic policies and I think it is unbecoming of a leader of such a great state to keep trying to interfere in other countries' domestic policies.'
He added: 'The president is right to be concerned about serious violence but he should be concerned about the serious violence in his own country where it is more than 10 times higher than it is in the UK.'
London's violent crime rate rate remains minuscule when compared with even the safer cities of the USA.
The murder rate in London is 1.5 per 100,000 of the population, low by comparison with the US
There were 132 murders in London last year, leaving the capital with a homicide rate of 1.5 per 100,000 residents.
The murder rate in St Louis is 64.9 per 100,000 residents, according to the Major Cities Chiefs Association Violent Crimes Survey, which is 43 times higher than London.
In Baltimore the murder rate is 51.1. In New Orleans it is 40.6 and in Detroit it is 39.7.
In Washington DC, home to Congress and the White House, the murder rate is 11 times higher than London.