Donald Trump said he would not deal with Britain’s ambassador to Washington after a leak of confidential memos in which the diplomat described the U.S. president’s administration as “inept”.

Trump also attacked Britain’s outgoing Prime Minister Theresa May, who had said her government had full confidence in ambassador Kim Darroch, criticizing her handling of Brexit and saying she disregarded his advice.

“What a mess she and her representatives have created,” he wrote on Twitter. “I do not know the Ambassador, but he is not liked or well thought of within the U.S. We will no longer deal with him. The good news for the wonderful United Kingdom is that they will soon have a new Prime Minister.”

The spat between the two close allies followed the leak to a British newspaper on Sunday of memos from Darroch to London in which he said Trump’s administration was “dysfunctional” and “diplomatically clumsy and inept”.

May’s spokesman said while Darroch’s opinions did not reflect the view of the government or ministers, he said the diplomat had London’s backing and ambassadors needed to have the confidence to give their frank assessments.

“Contact has been made with the Trump administration, setting out our view that we believe the leak is unacceptable,” May’s spokesman told reporters. “It is, of course, a matter of regret that this has happened.”

May is also due to leave office before the end of the month and has previously clashed with Trump over a number of issues from Brexit to the Iran nuclear deal.

However, the timing of the discord comes as Britain is hoping to strike a major trade deal with its closest ally after it leaves the European Union, an exit scheduled for Oct. 31.

The two contenders to replace May, former London mayor Boris Johnson and foreign minister Jeremy Hunt, have both indicated they could support leaving the EU without a deal, making a future agreement with the United States even more important.

Trade minister Liam Fox, who was visiting Washington this week, said he would apologize to Trump’s daughter Ivanka whom he was due to meet during his trip.

‘SERIOUS CONSEQUENCES’ FOR LEAKER

In confidential memos to his government dating from 2017 to the present, Darroch had said reports of in-fighting in the White House were “mostly true” and last month described confusion within the administration over Trump’s decision to call off a military strike on Iran.

“We don’t really believe this Administration is going to become substantially more normal; less dysfunctional; less unpredictable; less faction riven; less diplomatically clumsy and inept,” Darroch wrote in one cable.

British officials have launched an inquiry to find out who was responsible for the leak and foreign minister Hunt promised “serious consequences” for whoever was responsible.

He told the Sun newspaper that the inquiry would consider whether the memos had been obtained by hacking by a hostile state such as Russia although he said he had seen no evidence for this.

Asked whether British spies would join in the hunt, Jeremy Fleming, the head of the GCHQ intelligence agency, told BBC radio: “I can’t get into the detail of the investigation. If they require our services then GCHQ will help.”

Christopher Meyer, a former British ambassador to Washington, said there was a “possible range of villains”.

“It was clearly somebody who set out deliberately to sabotage Sir Kim’s ambassadorship, to make his position untenable and to have him replaced by somebody more congenial to the leaker,” he told BBC radio.

Nigel Farage, leader of the Brexit Party and long a thorn in the side of British governments, said figures such as Darroch would be “not be around” if Johnson, the favorite to replace May, was selected by Conservative Party members.

However, former British foreign minister William Hague said Darroch should not be removed from his post, pointing out that no U.S. diplomats had been withdrawn from their roles after the mass release of secret U.S. cables by WikiLeaks in 2010 which included highly critical appraisals of world leaders.

“You can’t change an ambassador at the demand of a host country. It is their job to give an honest assessment of what is happening in that country,” Hague told BBC radio.

May’s spokesman said police would be involved if there was evidence that the leaker had committed a crime.

Two months ago, May fired defense minister Gavin Williamson after secret discussions in the National Security Council about Chinese telecoms firm Huawei were leaked to the media, and an inquiry concluded that he was responsible.

Williamson denied any involvement and police said there was no reason for a criminal investigation.