Boris Johnson and Jeremy Hunt condemned Donald Trump on Monday night for his comments about a group of Democrat congresswomen amid an escalating racism row in the US.
Theresa May earlier issued a parting shot at the US president as she prepares to leave office, calling Mr Trump's remarks "completely unacceptable" after he told a group of minority ethnic congresswomen to "go back" where they came from.
It came as Nancy Pelosi, the Democrat House Speaker, said she would introduce a resolution in Congress this week to formally censure the president for "xenophobic tweets."
Mr Trump doubled down on his remarks on Monday, accusing the congresswomen of "hating our country," probably being communists, and suggesting they should leave the United States.
The row began on Sunday when targeted the four high profile, liberal, female Democrats, who are known as "the squad" and have been critical of his immigration policies.
....and viciously telling the people of the United States, the greatest and most powerful Nation on earth, how our government is to be run. Why don’t they go back and help fix the totally broken and crime infested places from which they came. Then come back and show us how....— Donald J. Trump (@realDonaldTrump) July 14, 2019
They are Ilhan Omar of Minnesota, Alexandria Ocasio-Cortez of New York, Rashida Tlaib of Michigan, and Ayanna Pressley of Massachusetts. All are US citizens and only one, Ms Omar, was born outside the US. She was born in Somalia and became a US citizen in her teens.
Speaking at the White House on Monday, Mr Trump said many people had "loved" his tweets telling them to leave the US.
He said: "These are people that hate our country. They hate it, I think, with a passion. I hear the anti-Semitic language, the hatred they have for Israel, the love they have for our enemies.
"If they're not happy here they can leave. I'm sure there will be many people that won't miss them."
He added: "As to whether or not they're communists, I would think they might be. This isn't what our country is about.
"If the Democrats want to gear their wagons around these four people they're going to have a very tough election."
Asked if he was concerned his tweets were being described as racist and praised by white nationalists, Mr Trump said: “It doesn’t concern me because many people agree with me.
“And all I’m saying is if they want to leave, they can leave.”
The president claimed that Ms Omar, the first black Muslim woman in Congress, "hates Jews" and "puffs her chest out" when she talks about al-Qaeda. Kamala Harris, a Democrat 2020 presidential candidate, said Mr Trump's remarks were "absolutely racist and un-American."
The four Democrat congresswomen later held a joint press conference at which they condemned Mr Trump's comments as "disgusting and bigoted," and called for him to be impeached.
Ms Omar said it was a "pivotal moment" and "the eyes of history are watching us."
Ms Ocasio-Cortez said: "He does not know how to defend his policies. So what he does is attack us personally."
The president gave a running commentary on Twitter during the press conference.
He wrote: "We will never be a Socialist or Communist Country. IF YOU ARE NOT HAPPY HERE, YOU CAN LEAVE!"
....They are anti-Israel, pro Al-Qaeda, and comment on the 9/11 attack, “some people did something.” Radical Left Democrats want Open Borders, which means drugs, crime, human trafficking, and much more....— Donald J. Trump (@realDonaldTrump) July 15, 2019
In the final debate of the Tory leadership contest on Monday night, Mr Johnson and Mr Hunt condemned Mr Trump's remarks.
Mr Hunt said: "I have three half-Chinese children, and they are British citizens born on the NHS, and if anyone ever said to them 'go back to China', I would be utterly appalled. And I would say something else, it is totally un-British to do that and so I hope that would never happen in this country."
Mr Johnson said: “You simply cannot use that language about sending people back to where they came from. That went out decades and decades ago and thank heavens for that.”
Neither would say the language was racist.
Earlier Mrs May's spokesman said: "Her view is that the language used to refer to these women was completely unacceptable." Mr Trump and Mrs May, who leaves office in just over a week, have had a roller coaster relationship.
Earlier this month they had a public falling out over the resignation of Sir Kim Darroch, the UK's ambassador to Washington, after his diplomatic cables were leaked.
The two leaders are not expected to speak again before Mrs May leaves Downing Street.
In the US, Lindsey Graham, the Republican senator, backed the president: "We all know this crowd are a bunch of communists and they hate Israel, they hate our own country."
Rudy Giuliani, Mr Trump's lawyer and a former New York City mayor, also rejected claims that the president was racist.
AOC, Tlaib and Omar criticize America so often and so viciously preferring Soviet, Chinese, Venezuelan socialism to our free market economy that saying they would be happier somewhere else is a fair response. To say it’s racist is almost as ignorant as their statements.— Rudy Giuliani (@RudyGiuliani) July 15, 2019
Most Republicans stayed silent on Mr Trump's divisive rhetoric, however, while several began expressing concern late on Monday.
House Republican Leader Kevin McCarthy said the four lawmakers belonged in the United States. "This is their country," he told reporters.
Texas Representative Will Hurd, the only African-American Republican in the House, called the attacks "racist" on CNN.
Tim Scott, the Senate's only black Republican, called them "racially offensive" on Twitter.
People can disagree over politics and policy, but telling American citizens to go back to where they came from is over the line.— Mitt Romney (@MittRomney) July 15, 2019
Others did not go that far. Senator Mitt Romney, the party's 2012 presidential nominee, and Senator Marco Rubio, who ran in 2016, both condemned the remarks but declined to characterize them as racist.
House Democrats plan for a vote this week on a resolution that "strongly condemns President Donald Trump's racist comments" that four congresswomen of color should return to their native countries.
The measure says Mr Trump's tweets "have legitimised and increased fear and hatred of new Americans and people of colour."
The four-page resolution quotes from a 1989 speech by President Ronald Reagan that said America draws its strength "from every country and every corner of the world." Reagan, a Republican, said that if the US ever closed its doors to immigrants, "our leadership in the world would soon be lost."
The Democrats' measure says the House is "committed to keeping America open to those lawfully seeking refuge and asylum."
House Republican Leader Kevin McCarthy said Democrats were playing politics.
New Zealand Prime Minister Jacinda Ardern joined international condemnation of Mr Trump's xenophobic tweets on Tuesday, saying she proudly celebrated her country's diversity.
"Usually I don't get into other people's politics, but it will be clear to most people that I completely and utterly disagree with him," Ms Ardern told Radio New Zealand.
Justin Trudeau earlier added his voice to those condemning the US president, saying "that is not how we do things in Canada."