LONDON — Boris Johnson agrees Donald Trump is undiplomatic but "can't dissent" with the U.S. president's damning verdict on Theresa May's handling of Brexit.

Speaking to POLITICO London Playbook as news broke on Wednesday that U.K. Ambassador Kim Darroch had resigned over his leaked cables on Trump, the man set to be Britain's next prime minister refused to echo much of the U.K. establishment's indignation at the president's leadership style.

The front-runner for the Conservative Party leadership spoke approvingly of Trump’s tweets about outgoing Prime Minister May’s "foolish" approach to Brexit.

“I can’t dissent from that,” he said with a chuckle, when told that Trump had called her deal a "disaster."

“When it comes to the context of what the president has said about the Brexit deal, I find it hard to disagree.

“He has strong views about Brexit and he has strong views about the deal. Probably, from the point of view of those of us who want to get Brexit done and make a great success of it, it would be fair to say this is a debate that’s best conducted within the U.K.," Johnson added. "But you know — the president has his style and his approach.”

“If Donald Trump can make friends with Kim Jong Un, then he can make friends with Kim Dar-roch" — Boris Johnson

Pressed repeatedly by POLITICO on whether it is right for a foreign leader to criticize a British prime minister in this way, Johnson eventually said: "I think most people feel … I don’t want anybody else telling us what to do. Or anybody else criticizing our government, I suppose is my feeling. But if you ask me whether I think the Brexit negotiations have been brilliantly handled, I don’t think so.”

Johnson, a former U.K. foreign secretary, is accused by senior Tory politicians — including a minister who worked under Johnson at the Foreign Office and now under his successor and leadership challenger Jeremy Hunt, of throwing veteran diplomat Darroch “under the bus" by not defending him against Trump.

Johnson protested that he had decried the leaks, and described himself as a "long-standing admirer of Kim Darroch." But he also made light of Trump's hostile words about the ambassador, saying: “If Donald Trump can make friends with Kim Jong Un, then he can make friends with Kim Dar-roch.”

He defended his refusal to use a TV debate on Tuesday to commit to keeping Darroch in his post if he becomes prime minister, saying: “I think it’s totally, totally wrong to drag the career prospects of a civil servant into a political debate.”

Turning to Brexit, which will be his biggest challenge if he takes up residence in Downing Street this month as expected, Johnson said the success of Brexit Party founder (and avid Trump fan) Nigel Farage in defeating the Tories in May's European election should help him negotiate a better deal with Brussels.

Johnson insisted he was not bluffing on Brexit and the EU should realize that no-deal preparations will start on day one of his premiership, adding: “They know we are serious.”

Listing reasons why the EU will renegotiate despite its repeated assurances that the Withdrawal Agreement cannot be reopened, Johnson said: “They [the Brexit Party] have now got 29 Brexit MEPs in the European Parliament.

"I’m not certain they [the EU] want to have Ann Widdecombe lecturing them about their deficiencies,” he added, referring to a famously cantankerous Brexit Party MEP.

Johnson denied his unpopularity with EU leaders would be a problem when negotiating an improved deal. “It’s not true. I had great friends in Brussels, I had great relations with people around the table at the European Council.”

Asked what would be his message to Germany's Angela Merkel, outgoing European Commission chief Jean-Claude Juncker, and other EU leaders, he said: “The United Kingdom is passionately pro-European, but we do not seek continued membership of the EU institutions and we want to leave.

“We want to devise a new partnership based on friendship and intensified bilateral relations with Germany, with France," Johnson added. "In some ways, I think the bilateral relations have been hollowed out because everything is done through Brussels. Let’s rebuild those partnerships, let’s be much more positive about it."