June 28 (UPI) -- Britain's most senior civil servant Mark Sedwill sent a letter to Prime Minister Boris Johnson on Sunday announcing he will resign in September.
Sedwill, 55, declared his intention to step down as cabinet secretary and head of civil service, while his role as national security adviser will be assumed by Johnson's chief adviser for Britain's plans to exit the European Union, David Frost.
"Two years ago, when my predecessor fell ill, your predecessor asked me to step in as cabinet secretary and you asked me to continue to support you through Brexit and the election period," he wrote. "It was obviously right to stay on for the acute phase of the COVID-19 crisis. As you are setting out this week, the government's focus is now shifting to domestic and global recovery and renewal."
Johnson responded to Sedwill in a letter of his own saying that he had made a "massive contribution" during his civil service.
As cabinet secretary, Sedwill was tasked with coordinating the work of permanent secretaries during the COVID-19 pandemic, supplies of personal protective equipment, food supplies, prison releases and coronavirus tests.
His departure follows weeks of negotiations regarding his role and reports of tension with Johnson and other members of his cabinet.
Deve Penman, secretary of the civil servants' union, accused other government officials of seeking to harm Sedwill's reputation, adding that the government would be "weaker as a result" of his departure.
"Not only is it a self-defeating and corrosive tactic, it's also a cowardly one, safe in the knowledge that those who are briefed against are unable to publicly respond," said Penman.