UK chief official Sir Mark Sedwill has confirmed that he plans to step down from office in September.
In a letter to Boris Johnson, he said it was the right time to go when the government advanced to the next phase of its coronavirus recovery plan.
His departure follows reports of tensions between him and senior members of Boris Johnson’s team.
The senior officials union, the FDA, said Sir Mark had been undermined in a “cowardly” way.
FDA Secretary General Dave Penman accused unidentified Downing Street officials of reporting against Sir Mark.
He added: “Not only is it a self-destructive and corrosive tactic, it is also a coward, safe in the knowledge that those who are informed cannot respond publicly.”
He said the government would be “weaker as a result” of Sir Mark’s departure.
Sir Mark’s other role as national security adviser will be taken over by Johnson’s chief Brexit adviser, David Frost.
Dominic Cummings, considered the prime minister’s most influential political adviser, has long called for public administration reform.
And in a speech on Saturday, Michael Gove attacked what he called “group thinking” within his ranks.
As Cabinet Secretary, Sir Mark advised the Prime Minister on the implementation of government policy and conduct.
A career diplomat, he served as ambassador to Afghanistan for a 20-year career at the Ministry of Foreign Affairs. He assumed the post of Cabinet Secretary in the short term after the death of Sir Jeremy Heywood in November 2018.
Previously, she had worked alongside former PM Ms. May as the highest ranking official in the Home Office.
After leaving government service in September, Sir Mark will become a couple while also chairing a new panel on global economic security when the UK takes over the presidency of the G7 economic group of nations.
Several of the top public officials have left their posts or are planning to leave in the coming months after the conservatives’ overwhelming electoral victory in December.
Philip Rutnam is suing the Interior Ministry for unfair dismissal after resigning in February, while Simon McDonald leaves the Ministry of Foreign Affairs in September after his merger with the Department for International Development.
‘Extraordinary times’
Sir Mark said he had served both Johnson and his predecessor in “extraordinary times”.
“Two years ago, when my predecessor became ill, your predecessor asked me to intervene as Cabinet Secretary, and you asked me to continue supporting you during Brexit and the election period,” he wrote.
“Obviously, it was correct to remain in the acute phase of the Covid-19 crisis. As proposed this week, the government’s focus is now shifting towards national and global recovery and renewal.”
There have been no secrets about the government’s ambition to shake up the way it does business.
And there has never been any mystery about the Prime Minister’s top adviser Dominic Cummings’ desire to change Whitehall.
What may have been rather abstract and hypothetical is becoming real.
Because it does not only matter who are the politicians who set the direction of the government. It’s not just important who your unelected advisers are who suggest, cajole, and promote your ideas.
Officials charged with carrying out their agendas are also crucial.
Sir Mark Sedwill’s departure, therefore, matters. The cabinet secretary is the chief of thousands upon thousands of public officials, and he has the ultimate responsibility for making the government machine work. And he is the third high-ranking official who has resigned from the Boris Johnson government.
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In response, Johnson said Sir Mark had made a “massive contribution” to public life in the past 30 years and that he had been a source of “cunning advice.”
“It has done everything in Whitehall: from Afghanistan to modernization of the civil service; from immigration policy to Brexit to the defeat of the coronavirus,” he said.
“After serving for decades with great distinction and unflappable good humor, I believe he has earned the nation’s gratitude.”
Shadow Shadow Cabinet Minister Helen Hayes paid tribute to Sir Mark, saying he had acted with dedication in “difficult times.”
But he added: “The day it was revealed that millions of jobs across the country could be threatened in the coming months, it is very worrying that Boris Johnson and Dominic Cummings are concerned about reorganizing Whitehall.”
No. 10 said that Frost would succeed Sir Mark as national security adviser, also taking a seat in the Lords, but that he would continue to oversee the negotiations on a trade agreement with the EU until its conclusion.