Trump's intervention comes at the end of a tumultuous few days for May.
The shadow policing minister, Labour MP Louise Haigh, said, "It has emerged that officers being accommodated in Essex are sleeping on cots in squash courts, 100 female officers with four toilets between them, likely to be sleeping on mats tonight, 300 male officers with five toilets between them".
Trump's suggestion that her Brexit plan will kill any such deal has given her opponents ammunition against her, and could potentially spark a chain of events that leads to her downfall. These will focus on relations with Russian Federation, trade, Brexit and the Middle East.
Trump's comments blaming immigration for crime in England were "preposterous", he added.
About 150 guests are understood to have agreed to attend the dinner at Blenheim Palace, including cabinet members and business leaders.
From left, first lady Melania Trump, President Donald Trump, British Prime Minister Theresa May and her husband Philip May watch the arrival ceremony at Blenheim Palace, Oxfordshire, Thursday, July 12, 2018.
British Prime Minister Theresa May will publish details Thursday of her long-awaited Brexit plan to restart talks with the European Union, after facing down a revolt by eurosceptic ministers that could still unseat her.
The US president said he would have done the Brexit negotiations "much differently" and claimed the Prime Minister did not listen to his advice, in an interview with The Sun.
"Mr. President, Sir Winston Churchill once said that "to have the United States at our side was, to me, the greatest joy", May told Trump, according to a text of her speech.
Fiat Chrysler workers strike over £99m Ronaldo football signing
As captain of the Portuguese team in the 2018 World Cup, he scored four goals, including a hat-trick against Spain. It's calling for a strike at the Melfi plant in southern Italy between 10 p.m. on July 15 and 6 p.m. on July 17.
Trump in London amid protests and Brexit turmoil
Mr Trump and his wife Melania arrived at Stansted airport, where he was met by the UK's worldwide trade secretary Liam Fox. It "delivers on the instruction we delivered loud and clear from the British people to take back control", he added .
Wont let Nawaz become a hero, says Imran
Sharif said the Pakistani people once again saw the "real face" of justice. [She is] still not conscious and on ventilator. Meanwhile in Pakistan, things don't look good for the beleaguered PML-N. "Shehbaz says their workers have been picked up".
"I think he has done a bad job on crime, if you look, all of the frightful things going on there, with all of the crime that is being brought in", Trump said, later adding that he thinks Khan has insulted him by not being "hospitable to a government that is very important".
"I think it's fine", he said.
Ahead of the visit as Trump was preparing to leave the North Atlantic Treaty Organisation summit, he said the United Kingdom was in turmoil. I get along with her very nicely.
While Mr Johnson may now be a backbencher, Mr Trump said he hoped he would still see the former foreign minister - another blow to the fragile position of Mrs May.
"Maybe they're taking a little bit of a different route [on Brexit], so I don't know if that's what they voted for", he told a press conference after the North Atlantic Treaty Organisation summit in Brussels.
He also added that Johnson, "would be a great Prime Minister".
He was met at Stansted Airport by dignitaries including International Trade Secretary Liam Fox and the USA ambassador Woody Johnson.
Trump has clashed in the past with May - even though she is a conservative who shares his view that defense spending should be raised - and with her predecessor, David Cameron, who challenged Trump's anti-Muslim campaign stance as "divisive, stupid and wrong".
"So I would imagine that's what they will do, but maybe they will take a little bit of a different route".
"I'd like to see them be able to work it out so it could go quickly", he said.