Britain's ambassador to Washington Kim Darroch's leaked emails, that had created controversy which led to his eventual resignation earlier this week, have brought a new statement to light in which Darroch has described Trump's withdrawal from Iran's nuclear deal as 'diplomatic vandalism'.
In the confidential emails, which got leaked to a local newspaper, Darroch had criticised US President Donald Trump as "inept, insecure and incompetent".
In the latest revelation, Darroch has alleged that Trump pulled out of the Iran nuclear deal because it was associated with his predecessor Barack Obama.
"The administration is set upon an act of diplomatic vandalism, seemingly for ideological and personality reasons -- it was Obama's deal," the ambassador wrote in a diplomatic cable in May 2018.
A British newspaper Sunday Times reported that a government investigation into the leak had identified a civil servant as the person responsible.
Working with officials from the National Cyber Security Centre, part of spy agency GCHQ, and MI6, the probe has homed in on a suspect who had access to historical Foreign Office files, the paper said.
The first leaked reports authored by Darroch were published last weekend, causing major turmoil between Britain and its closest ally.
Darroch, who had resigned on Wednesday, saying it was now "impossible" to do his job.
Donald Trump had reacted to the leaked emails and had called Darroch a "pompous fool" whom he would no longer deal with.
Darroch, in the fresh set of leaked emails, indicated there were divisions in Trump's team over the decision and criticised the White House for a lack of long-term strategy.
"They can't articulate any 'day-after' strategy; and contacts with State Department this morning suggest no sort of plan for reaching out to partners and allies, whether in Europe or the region," he wrote.
In 2015, the United States, China, Britain, France, Russia and Germany signed a deal with Iran to limit its nuclear programme in exchange for a partial lifting of international economic sanctions.
Trump had long been critical of the deal and withdrew the United States on May 8, 2018.