Controversy over US President Donald Trump's attacks on London's mayor moved to the centre of the campaign to replace Prime Minister Theresa May on Monday after a leading candidate endorsed the intervention.
Jeremy Hunt, the Foreign Secretary, said Mr Trump's concern over knife attacks and other crime in London was echoed by many, including himself.
“President Trump has his own style," Mr Hunt said at a campaign meeting.
"I wouldn’t 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 spent more time on politics than the actual business of making London safer.
"And in that, I 150 per cent agree with the president."
Mr Trump had tweeted a message from the right-wing commenter Katie Hopkins, who used the trope "Londonistan" to decry Sadiq Khan's leadership of the city.
"London needs a new mayor ASAP," he said. "Khan is a disaster. Will only get worse."
There has been support from across the political spectrum for Labour's Muslim mayor.
But Mr Hunt's comments ensure that Mr Trump's comments will be put to every Conservative candidate as the election moves into elimination rounds on Tuesday and Thursday.
Mrs May repudiated the US president's remarks.
"The prime minister would not retweet Katie Hopkins, nor use that language," her spokesman said.
"The prime minister agrees with the mayor that knife violence should have no place in London or anywhere else in our country."
Home Secretary Sajid Javid also decried Mr Trump's attacks.
“It’s unbecoming to the leader of such a great state,” Mr Javid said. “He should be concerned about serious violence in his own country, which is 10 times higher than in the UK.”
The six remaining contenders for the leadership will learn on Tuesday who has survived the race to make a short list of two, which will be voted on next month by party members.
In the first rounds the 313 Conservative MPs vote in stages on the contenders.
Runaway favourite Boris Johnson, who is a former foreign secretary and mayor of London, was endorsed by cabinet minister Matt Hancock on Sunday night.
Mr Johnson, the face of the official Brexit campaign in the 2016 referendum, won the backing of 114 MPs in the first round.
Sterling has fallen to six-month lows as his hold on the campaign has grown stronger after he promised to lead the UK out of the EU with or without an agreement by the end of October.
"It looks like Boris Johnson is going to be the next prime minister unless there is a big surprise and that indicates a looming confrontation with the EU," said Lee Hardman, a strategist at MUFG in London.
The chances of a disorderly Brexit were assessed to have risen to 25 per cent in a June Reuters poll, up from 15 per cent in May.
The pound weakened a third of a per cent to $1.2554 against the dollar, its lowest level since a January crash.
Against the euro, the pound weakened to a five-month low of 89.43 pence.
Outsider candidate Rory Stewart continues to gain ground on more recognised candidates through a social media-powered campaign.
In contrast to Mr Johnson, Mr Stewart has vowed to do everything he can to prevent a chaotic break-up with the EU.