Britain’s effort in Libya has been “extraordinarily successful”, Liam Fox said today.

The British defence secretary gave an upbeat assessment of the UK’s involvement in the protracted Libya campaign despite concerns among MPs about the duration of the mission authorised by the United Nations in March to protect Libyan civilians from Colonel Muammar Gaddafi’s forces.

Fox insisted again that last year’s Strategic Defence and Security Review would not be reopened and that continued overseas missions for the British military were likely.

In Libya, the UK’s commitment and the danger to British forces recently has increased further with the recent deployment of Apache helicopters.

Speaking about the review Dr Fox said: “We knew that we would get a test, I wasn’t quite expecting the test to come so quickly as it came with Libya, but we said in our SDSR we would be able to carry out one long enduring mission like Afghanistan – when we have a core force of 9,500 but regularly 11,000 or more actually on the ground.

“And we said we would also be able to carry out one shorter programme – meaning one of about six months’ duration – and we have been, I think, extraordinarily successful with what we have done in Libya.

“We were able through Nato to stand up with command and control, we were able to get our assets moving very quickly, we were more than capable within the limitations we had to get our air power projected… to ensure that we had Typhoon and Tornado performing very effectively, of course very recently adding in our Apache attack helicopters.

“We set the pace in Libya and we have been driving very much of the military process.”

Speaking to a conference organised by Conservative Intelligence, which provides advice on Tory thinking, Dr Fox said the review – cutting billions of pounds from the over-committed Ministry of Defence budget – would not be revisited.

“When people say to me ‘should we reopen the SDSR?’ I say to them what you really mean is you want to spend more on defence,” he said.

“And that’s fair enough to say that, but if you want to tell me what taxes you want to raise and tell me what cuts you want to make to other programmes, because you can’t increase borrowing without severely affecting Britain’s long-term strategic position.

“It’s a tough message but it’s something that we have to face because if we don’t face it then we don’t have the economic power on which influence is built and there is no better way to secure the future than to shape it.”

The Defence Secretary stressed his support for the Government’s increase to the aid budget despite controversy last month over a leaked letter in which he challenged the idea to put the commitment on a statutory footing.

But Dr Fox pointed out that the increase was in the Tories’ election manifesto and was combined with an ambition to spend the money better.

“When we made our decision to increase, as we did in our manifesto, the proportion of our GDP spent on aid, that was done on the basis that that aid could be spent in a different way, in a better way, more able to be involved in prevention of conflict and stability than it had been in the past,” he said.

International development secretary Andrew Mitchell acknowledged that the arguments for aid were “more difficult to get across in a time of financial austerity”.

But he said his job was to convince the British people of the value of spending on aid.

“My ambition is that over the next four years people will come to think, across our country, of Britain’s fantastic development work with the same pride and satisfaction that they see our great institutions like the Armed Forces and the monarchy,” he said.

“This is brilliant work that Britain is doing.”