Lord West was accused of bragging after telling The Sunday Telegraph there had been a "dramatic improvement" in the UK's security since the Prime Minister took over in June.

"I think we're ahead of all countries in the world on the protection front, which is great," he said.

He said the measures outlined on Wednesday to improve defences at airports, train stations and other public places represented part of a "step change" in approach.

The former head of the Royal Navy, appointed to Mr Brown's Government of "all the talents" in the summer, also expressed regret for his apparent stand - later humiliatingly reversed - against the extension of pre-charge detention.

He was forced to "clarify" his comments within an hour of telling BBC Radio 4's Today programme he had yet to be convinced of the need for a longer detention period for terror suspects.

The former First Sea Lord later suggested he was a "simple sailor" who had failed to make himself properly understood the first time.

In the latest interview, he denied being "hauled in" by the Prime Minister for a ticking off, saying he attended Number 10 for a pre-arranged breakfast.

He went on: "The reason I think I was most upset on Wednesday was because so many people had worked so hard and achieved so much. We have really made a step change I believe. That was the message that I was keen to let the Prime Minister put across and I thought I had let people down."

Liberal Democrat home affairs spokesman Nick Clegg said: "First Lord West flip-flops over 28 days, then he brags about Britain's preparedness. This is not the way to improve public confidence in national security."