THERESA May has revealed Donald Trump advised her to sue the European Union over Brexit rather than negotiate with its leaders.

The US president caused a major diplomatic row when he said in an interview published on the eve of a meeting with the Prime Minister on Friday that she had not followed his suggestions in dealing with the bloc, and that her Brexit plans would “kill” hopes of a trade deal with the United States.

“I would have done it much differently. I actually told Theresa May how to do it but she didn’t agree, she didn’t listen to me,” Trump said in an interview published in The Sun on Friday.

He later disowned the comments, accusing the tabloid of “fake news” and insisting that a deal could still go ahead. However, he stopped short of revealing his advice to the Prime Minister, saying that May “found it too brutal”.

But the issue came up again yesterday, with May being pressed on what the advice was when she appearing on BBC1’s The Andrew Marr Show.

“He told me I should sue the EU, not go into negotiation, sue them,” she said. “What the president also said at that press conference was ‘Don’t walk away. Don’t walk away from the negotiations. Then you’re stuck’.”

May’s blueprint for future relations with the EU, unveiled last week, proposes a softer Brexit, including a “common rule book” over the trade of goods.

It also sets out plans for a treaty to be signed committing the UK to “continued harmonisation” with EU rules – which she believes would avoiding friction on the Irish border – and that Westminster should oversee the UK’s trade policy, and have the ability to “choose” to diverge from the EU rules.

However, the proposals have enraged hardline Brexiteers, prompting the resignation of David Davis and Boris Johnson from her Cabinet, as well as junior Brexit minister Steve Baker. Ministerial aide Robert Courts resigned yesterday, becoming the third parliamentary private secretary to do so since the Chequers compromise plan was drawn up.

Amid mounting anger in her party, May yesterday insisted the blueprint represented a “good deal” for the UK, while acknowledging she had been forced to make changes to her original plans over the Irish border by the EU.

She said: “This is a good deal for the UK. In this one area we needed to make a change – the question of trade in goods in relationship to the frictionless border – we needed to make a change. We needed to come forward with another option in order to ensure that we can get those negotiations on trade. The clock is ticking.”

During the interview she denied claims by Davis that he had been “cut out” of the plan and therefore had no choice but to resign. She also rejected suggestions it would prevent the UK striking free trade deals around the world.

May is expected to face further turmoil this week.

Reports yesterday suggested Johnson is being urged to give a resignation speech in the Commons – which Brexiteers hope will lead to letters to the backbench 1922 Committee to spark a vote of no confidence in May.

A total of 48 letters are needed for such a move and it is believed the committee’s chairman has received close to 40 to date.

However, it was also reported that Johnson may now be regretting his decision to step down, with one ally saying he was enduring a “black dog” of depression and was “sitting around in his pants wondering if he’s done the right thing”.

Meanwhile, Tory Brexiteer Jacob Rees-Mogg issued a fresh warning to the Prime Minister to change tack on her blueprint for leaving the EU or see her party split.

Interviewed on BBC1’s Sunday Politics programme, he played down the prospect of an immediate leadership challenge, and said May had the opportunity to change her policy which would have to be brought before Parliament.

“The Prime Minister will have a choice then. She’ll have to decide either to change the policy or get it through on the back of Labour Party votes and that would be a very divisive thing for the Conservative Party to do,” he said.