Donald Trump is “trying to humiliate and belittle” Theresa May, Labour’s Shadow Foreign Secretary has warned – blaming her “bad judgement” for the crisis.

Emily Thornberry said the Prime Minister had made the error of “trying to be friends” with the US President, in her desperate search for a post-Brexit trade deal.

Yet, overnight, Mr Trump had taken to Twitter to tell Ms May to keep quiet, after she described his re-tweeting of Britain First as “wrong”.

Ms Thornberry said that – while the UK should “always have good working relations with the US - Ms May should have recognised that “we don’t share values with this man”.

“How did we ever get into this situation? Because of bad judgement exercised by the Prime Minister,” she told BBC Radio 4’s Today programme.

And she added: “Despite all the political capital she has expended - and she tried to get a good relationship with this man - he is trying to humiliate and belittle in the way that he is and has been overnight.”

Ms Thornberry added that Mr Trump's tweets had put the Queen in a “very difficult and invidious position” because she would be his host for the planned state visit.

“The invitation wasn't Theresa May's invitation to make. The invitation technically comes from the Queen.

“If he comes next year, a year which is supposed to be a really happy year for the royal family, what on earth are people supposed to make of it?

“Of course, the whole thing will be a total security nightmare if Donald Trump comes over.

The Shadow Foreign Secretary said she was “very pleased” to see Ms May “stand up to him at last”, adding: “The Prime Minister was absolutely right to criticise.

But she pointed out other issues where the US was pursuing a different approach, including Mr Trump’s “constantly shifting position on Nato, trying to undermine climate change agreements, threatening the deal with Iran”.