Jeremy Hunt has suggested a career diplomat should replace Sir Kim Darroch as ambassador to Washington as the row over leaked diplomatic cables threatened to engulf the Brexit party.

Isabel Oakeshott, the journalist who provided a string of new revelations from the cables in the Mail on Sunday, denied that her partner, Richard Tice, the chair of the Brexit party and a newly elected MEP, had any sight or knowledge of the leak before it was published.

Tice has argued Darroch’s replacement should be “a pro-Brexit businessman who can do what is vital” including repairing ties with the US president, Donald Trump, and seeking a post-Brexit trade deal.

Speaking to BBC Radio 4’s Broadcasting House, Hunt suggested the Foreign Office would look at experienced diplomats to fill the post.

“I think that one of the best things about our diplomatic service are the skills acquired over many years by career diplomats, and Sir Kim Darroch exemplified that,” the Tory leadership contender said. “And we have some outstanding candidates who do have that experience, and we’ll obviously look at them.”

The foreign secretary said he defended the right of the media to publish leaked information, “however uncomfortable it can be sometimes, if they judge it to be in the public interest”.

The Mail on Sunday published further memos from Darroch on Sunday, defying a much-criticised police warning that publishing further leaked documents could be a criminal act.

Johnson failed Kim Darroch abysmally. He doesn’t deserve to choose the next envoy to the US | Malcolm Rifkind Read more

According to the memos, Darroch had suggested in May 2018 that Trump had decided to unilaterally withdraw from the Iran nuclear deal for “personality reasons”, because it had been agreed by his predecessor Barack Obama. Darroch said in the cable that the Trump administration was “set upon an act of diplomatic vandalism”.

A Foreign Office spokesman said the perpetrator “should face the consequences of their actions” and said it was already the case that the UK and US had differences over the Iran nuclear deal.

“It’s not news that the US and UK differ in how to ensure Iran is never able to acquire a nuclear weapon; but this does underline that we do not shy away from talking about our differences and working together,” the spokesman said.

Reports suggested an investigation had identified the potential leaker, ruling out the possibility of a computer hack by a foreign state. Counter-terrorism police have launched a criminal inquiry.

“They think they know who did the leaking,” an unnamed government source told the Sunday Times. “It’s now a case of building a case that will stand up in court. It was someone with access to historical files. They went in and grabbed a range of material. It was quite crude.”

Profile Sir Kim Darroch Show Hide Born in County Durham in 1954, Sir Nigel Kim Darroch graduated with a degree in zoology from Durham University after attending Abingdon school on a scholarship. Tall and gregarious, he was nicknamed “Kimbo” at the Foreign Office, where he began his civil service career in 1977 and climbed the ranks of diplomacy in postings from Japan to Italy. He entered the public eye when he was frequently seen at Cameron’s side as his national security adviser from 2012 to 2015, joining him on trips to war zones, and chairing meetings on international crises, from Russian aggression in Ukraine to the collapse of the Libyan government. But it is his roles prior to that, as Blair’s top adviser on Europe, and as the permanent representative to the EU under Brown, that led to his vilification by Conservative Brexit supporters, who regard him as an arch Europhile. In January 2016 he took up the role of HM ambassador to the United States. Despite having been appointed when Hillary Clinton was thought likely to win the presidency, Darroch threw himself into courting Trump’s inner circle, “flooding the zone” of people in Trump’s orbit, hoping to gain influence through showing up and cultivating contacts. He also worked hard to court well-connected American journalists so he could benefit from their insights. In July 2019, Darroch resigned as ambassador, after a series of leaked diplomatic messages revealed that he had described the administration as "inept" and "clumsy". This led to a vocal Twitter outburst from Trump. Darroch could never have imagined that his distinguished 40-year diplomatic career would end with a US president publicly volleying insults his way, calling him “a very stupid guy”, “wacky” and “pompous fool”. Rowena Mason in London and David Smith in Washington Photograph: Niall Carson/PA

Hunt said the leaker should turn themselves into the police. “The leaker did something that was totally wrong. I’m not defending what was done. It’s caused damage to our relations with our closest ally,” he added.

“It’s caused one of our most esteemed diplomats to step down from his job. So I don’t defend that for one second. And I think they should cooperate with the police, yes.”

The shadow foreign secretary, Emily Thornberry, also defended newspapers’ right to publish leaked documents, but said the Conservative leadership frontrunner, Boris Johnson, should bear the brunt of the blame for Darroch’s resignation, for not offering him adequate support.

“It’s newsworthy. Any journalist would have published that,” she said. “It was wrong for it to be leaked, it was wrong for President Trump to throw a wobbler and behave like a toddler, it was wrong for Theresa May to be as weak as she was but the real villain of the piece is Boris Johnson who refused to stand with one of our most senior diplomats. That is not the way to behave.”

Thornberry, who on Sunday addressed a People’s Vote rally in Johnson’s Uxbridge constituency, told the crowd Johnson posed a threat to the country because of the relationship with Trump.

“Boris Johnson was the worst, the laziest, the most incompetent Minister I have ever had to shadow during my time in parliament, but also the most dangerous,” she told the rally, the first pro-referendum event she has addressed as shadow foreign secretary.

“And if his ‘do or die’ words on Brexit this week weren’t enough of a warning about the danger he poses to our country, then this week we got the biggest warning yet with his treatment of Sir Kim Darroch: a man who has been forced to resign from his job, simply for doing his job. Thrown under the bus by Boris Johnson in the most shameless, craven and cowardly act of servitude I have ever seen in politics.”