New key security adviser decision by Government slammed as 'misapplied persistent experiment'

It was announced on Sunday that Sir Mark Sedwill would be replaced by David Frost, who had been heading up Brexit negotiations with the EU.

But the decision has come under harsh scrutiny as unlike previous holders of the post, Mr Frost is a political adviser rather than a career civil servant - who also lacks security experience.

Leeds Central MP Labour Hilary Benn, who also chairs the Commons Future Relationship with the European Union Committee, said the decision was “a case of misapplied persistent experimentation” as he questioned how Mr Frost could both make Brexit negotiations his “top single priority” and oversee the nation’s security at the same time.

And Mrs May rounded on Cabinet Office minister Michael Gove in the Commons to explain the decision.

She said: "I served on the National Security Council for nine years - six years as home secretary and three as prime minister.

"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 added Brexit negotiations were “accelerating at the moment as both sides seek to find a conclusion over the course of the next 12 weeks”.

Rother Valley Conservative Alexander Stafford sought assurances that the changes would not “lead to delays and disruptions to implementing the Government's levelling up agenda”.

Mr Gove said: “We need to make sure that we reform how Government works in order to best deliver for the people whose taxes we spend.”