According to the Daily Mail on Saturday, the former ambassador said Donald Trump seemed to be discarding the Iran nuclear deal for "personality reasons," as the deal had been agreed to by former President Barack Obama.
The paper also reported that Darroch hinted at discord brewing between Trump's closest aides and said the White House had failed to produce a "day-after" plan on how to handle the aftermath of withdrawing from the deal.
Trump said Monday that the White House would no longer deal with Darroch, and the UK Foreign Office announced Darroch's resignation Wednesday. The former ambassador made his decision to step down after seeing that Boris Johnson, the current frontrunner to replace Theresa May as British Prime Minister, had refused to support him during Tuesday night's leadership debate, a British government official said.
A UK Foreign Office spokesman told CNN on Saturday that whoever leaked the cables "should face the consequences of their actions."
Police in the UK have opened a criminal investigation into the leaked diplomatic cables that led to Darroch's departure. Metropolitan Police Assistant Commissioner Neil Basu said Friday that there is a "clear public interest in bringing the person or people responsible to justice."
At the time the US withdrew from the deal, senior Trump administration officials -- including Secretary of State Mike Pompeo and the Director of National Intelligence Dan Coats said Iran was adhering to its commitments under the deal.
Earlier this week, Trump tweeted that Iran "has long been secretly 'enriching'," a claim that has been contradicted by the International Atomic Energy Agency, whose monitors were tasked with ensuring that Iran was complying with the terms of the 2015 deal, as well as by independent experts and by Trump's own top intelligence officials.
In May 2018, Trump pulled his country out of the JCPOA.
Iran and the remaining parties launched talks to save the JCPOA after the US withdrawal, but the three EU parties to the deal (France, Britain, and Germany) have failed to ensure Iran’s economic interests.
The EU’s inaction forced Tehran to stop honoring certain commitments to the nuclear deal, including a rise in the stockpile of enriched uranium.
Iran maintains that the new measures are not designed to harm the JCPOA, but to save the accord by creating a balance in the commitments.