US President Donald Trump used a joint press conference with UK Prime Minister Theresa May to excoriate Europe's migrant problem, calling immigration "very negative" and saying that Europeans "better watch themselves".
Mr Trump sees the European Union as a trade predator on the USA and also warned that immigration has been "very bad" for Europe and is changing the culture of the continent.
She touted the UK's "proud history of welcoming people who want to come to our country to contribute to our economy and our society".
"What is important is that we have a set of rules that enables us to determine who comes into our country", she said.
In an interview with The Sun newspaper on Thursday, Trump singled out London Mayor Sadiq Khan for critcisim, claiming he "has done a very bad job on terrorism". "When you are in another person's country you are a guest", Clarke said.
Trump continued: "It's a very sad situation". Europe is a place I know very well and what has happened has been very tough. "Look, in Europe, with their open borders, they don't have so much as an illegal immigration issue, they have an uncontrolled immigration issue and it's been a disaster for them", Clarke said on Newsmax TV's "America Talks Live".
"I just think it's changing the culture. Cultures do not blend, cultures clash, so if you don't control that sort of thing, your own culture will get run over and that's what President Trump is talking about".
President Trump arrives at Chequers in Aylesbury, England on Friday.
"The wonderful thing about our city is the diversity".
"I was very surprised and saddened that he was getting out of government", Trump said of Boris Johnson, adding that he would "make a great prime minister".
In a separate interview with BBC radio on Friday, Khan called Trump's claims "preposterous".
Trump also repeated criticism of US immigration laws, which he unsuccessfully lobbied the Republican-controlled Congress to change. But he said European countries need to "watch themselves".
Earlier this year, Trump was reported to have derided protections for immigrants from Haiti, El Salvador, and African countries.
But despite the strong anti-immigration language, more reminiscent of far-right protesters than a sitting president, Trump supporters in London for the "carnival of resistance" said the President was right to voice concerns.
Trump's comments while overseas highlight his hardline immigration rhetoric that he often uses on the campaign trail, often linking it to increased crime, citing the gang MS-13. The White House recently reversed course on a "zero tolerance" policy at the southern border, when immigration authorities were separating migrant children from their parents.
Trump also brought a similar immigration message to the North Atlantic Treaty Organisation summit in Brussels.
"If they do a deal like that, we would be dealing with the European Union instead of dealing with the United Kingdom, so it will probably kill the deal", he said. "And I said that loud and clear".