Former prime minister Theresa May has publicly challenged Boris Johnson’s decision to give the post of national security adviser (NSA) to a political ally with “no proven expertise” in the field.

In a dramatic intervention in the Commons, Mrs May said she had valued the “expert, independent advice” she had been given while on the National Security Council.

The current NSA Sir Mark Sedwill is being replaced by David Frost, a political appointee rather than a civil servant, in a move which has been met with hostility from diplomatic and security circles.

Former NSA Lord Ricketts said the move suggested the Prime Minister values “political loyalty” higher than “expertise and experience”.

In the Commons, a stern-faced Mrs May questioned Cabinet Office Minister Michael Gove about the appointment.

“I served on the National Security Council for nine years – six years as home secretary and three as prime minister,” she said.

“During that time, I listened to the expert independent advice from national security advisers.

“On Saturday (Mr Gove) said: ‘We must be able to promote those with proven expertise.’

“Why then is the new national security adviser a political appointee with no proven expertise in national security?”

Mr Gove responded: “We have had previous national security advisers, all of them excellent, not all of them necessarily people who were steeped in the security world, some of whom were distinguished diplomats in their own right.

“David Frost is a distinguished diplomat in his own right, and it is entirely appropriate that the prime minister of the day should choose an adviser appropriate to the needs of the hour.”

He insisted Mr Frost “is an expert” given his experience in diplomatic service.

Mr Frost is currently Mr Johnson’s Europe adviser, leading negotiations with the EU on a post-Brexit trade deal.

Sir Mark Sedwill
Sir Mark Sedwill (House of Commons/PA)

Sir Mark is also stepping down as Cabinet Secretary and head of the Civil Service, amid reports of clashes with Mr Johnson’s chief adviser Dominic Cummings.

He had been appointed as NSA when Mrs May was prime minister and had previously been at the Home Office when she was home secretary.

For Labour, shadow home secretary Nick Thomas-Symonds said the political appointment  takes the Government into “dangerous territory”.

SNP home affairs spokeswoman Joanna Cherry said the decision to replace Sir Mark is all about the “revenge” of the Vote Leave campaign.

House of Commons
Cabinet Office minister Michael Gove answers a question from former PM Theresa May about the new national security adviser (House of Commons/PA)

Yvette Cooper, Labour chairwoman of the Home Affairs Committee, asked: “Will the new politically-appointed special envoy national security adviser be responsible for the performance reviews of the heads of MI5, MI6 and GCHQ?”

Mr Gove stressed that reviews are carried out “in a way which is free of any taint of political interference”.

Lord Ricketts, in a commentary written for the Royal United Services Institute defence think tank, said: “Those advising ministers on national security do need the mastery of deep knowledge at a time when the Government is formulating a new national strategy in a dangerous world.

“But the message of Frost’s appointment is that the prime minister accords absolute priority not to expertise and experience, but to political loyalty among his closest advisers.

“That is not a reassuring conclusion.”

Concerns about Mr Frost’s appointment were also raised in the House of Lords.

Former ambassador to the US Lord Kerr of Kinlochard said: “Watching Washington provides a daily lesson on the perils of the politicised public service and the Iraq Inquiry reminded us of the dangers when politics and intelligence assessment overlap.”