"It's a national disgrace, the president of the United States is the best president ever", she said.
When asked about Mr Corbyn, the United States president said he did "not know him, never met him, never spoke to him", adding: "He wanted to meet today or tomorrow and I decided I would not do that". He was conducting a news conference, alongside Theresa May, when he let rip at Corbyn.
She signalled Iran and the Paris Climate Agreement as notes of difference. Emily Thornberry, Labour's foreign affairs spokeswoman, said Trump was "a sexual predator" and a racist who did not deserve the honor of a state visit hosted by Queen Elizabeth II.
Trump didn't seem to understand and answered with comments on London Mayor Sadiq Kahn, with whom he has had an ongoing feud. "It will be a very fair deal and I think that this is something that your folks want to do, my folks want to do, and we want to do and we're going to get it done".
I don't suppose the President meant to embarrass her. May and her officials at No. 10 Downing Street. "Great love all around". "Already starting to talk!"
His three-day visit began on Monday with a handshake with Queen Elizabeth II on the lawn of Buckingham Palace and a white-tie banquet featuring almost 200 royal and Trump family guests.
Outside, protesters against Mr Trump flew a giant inflatable blimp depicting him as a scowling baby in a nappy while others unveiled a statue of him tweeting while sitting on the toilet.
"I don't exactly know what your timing is, but stick around".
The Trump-May meetings come at an awkward moment.
May will step down as Conservative Party leader on Friday over her inability to deliver Brexit despite focusing on little else in three years on the job.
She will stay on as prime minister until her successor is chosen out of 11 contenders from her party. The leaders' top priority is a possible bilateral trade deal to take effect once - or if - Britain leaves the European Union. Also present: Secretary of State Mike Pompeo, Treasury Secretary Steven Mnuchin, and the president's daughter Ivanka Trump.
Demonstrators protest against the visit of US President Donald Trump in London.
It is notable that opposition Labour Party leader Jeremy Corbyn will address the crowds.
"Trump detests the old guard in the United Kingdom and at the moment this old guard is symbolised by lame duck Prime Minister Theresa May", Garrie said. "It's not unlike cartoons in a newspaper - it just so happens to be 3-D and floats in the air".
It is traditional for US and other world leaders to not weigh in on another's domestic politics.
Anti Trump protest in London.
After a day of pomp and pageantry involving the British royals, today was a day for politics and protests.
She will stay on as prime minister until her successor is found among 13 contenders who must make some hard choices before the twice-delayed Brexit deadline on October 31.