Gordon Brown today insisted British troops have the resources and equipment needed to take on the Taliban, as he paid tribute to eight soldiers killed in 24 hours last week.

The Prime Minister acknowledged the last few weeks had been "a sad and difficult time" for Britain, but said it was right to persist with the effort to prevent al Qaida from using Afghanistan as a base for worldwide terror.

Funding for Afghanistan from Treasury reserves has grown from £700 million to more than £3 billion since 2006, while helicopter capacity has increased by 84%, he said.

Mr Brown's comments came after a bloody start to July, which has seen 15 deaths, bringing the total number of UK military fatalities in Afghanistan since 2001 to 184 - surpassing the 179 who died in Iraq.

The deaths sparked fresh claims that British troops lack the necessary numbers and equipment for their mission.

Conservative leader David Cameron today said the lack of helicopters was "an extreme emergency" and urged the Prime Minister to "beg, borrow or steal" more from Nato allies.

In a statement to MPs, Mr Brown acknowledged British troops were facing "a tough and dangerous battle" as they take the fight to the Taliban in an operation codenamed Panther's Claw, designed to clear insurgents out of central Helmand province.

"It has been a difficult time and it is not over yet," said the Prime Minister, who today paid a private visit to the RAF Benson airbase in Oxfordshire to see Merlin helicopters which are to be deployed by Christmas.

"If we are to deny Helmand to the Taliban in the long term, if we are to defeat this vicious insurgency and in doing so make Britain and the world a safer place, then we must persist with our operations in Afghanistan.

"I am confident that we are right to be in Afghanistan, that we have the strongest possible plan and we have the resources needed to do the job."

Mr Brown said the goal of British troops remained the same as in 2001 - to prevent attacks in Britain and around the world by dealing with a "crucible of terror" in the border area of Afghanistan and Pakistan.

"I have been reassured by commanders on the ground and at the top of our armed services that we have the manpower we need for the current operations," he told MPs. "As the Chief of Defence Staff has said, the British armed forces are better equipped than they have been at any time for 40 years. But we are not complacent."

The UK's current 9,100-strong deployment will be reviewed following the presidential elections in the country in August, said Mr Brown. MPs will have a chance to discuss policy on Afghanistan at a special debate called in the Commons for Thursday.

Mr Cameron told MPs: "The Prime Minister talks about the increase in helicopter capability since 2006, but the number of troops has doubled since 2006, so proportionately there hasn't really been an increase in helicopter capability at all.

"Helicopters alone are not enough and helicopters are not invulnerable, but the former Chief of Defence Staff Lord Guthrie has said very clearly that more helicopters would save lives. Doesn't more need to be done right now?"

Mr Brown said the numbers of helicopters available to troops in Afghanistan had increased by 60% since 2006, while the provision of additional crews and equipment had increased their capability by 84%. Meanwhile, the Government had spent more than £1 billion on urgently-needed equipment, including 280 Mastiff vehicles offering "world-leading protection" against the mines and roadside bombs which have caused a majority of recent British deaths.

Merlin helicopters and Ridgeback armoured vehicles will be deployed in Afghanistan this year, he said.

But shadow defence secretary Liam Fox highlighted official Ministry of Defence figures suggesting less than half of the UK's helicopter fleet was fit for frontline operational or training purposes last month, largely because of routine maintenance.

"Of 507 military helicopters in service, only 43% were fit for purpose in June," said Dr Fox. "And fewer than half of our Chinooks were fit for purpose, when they are crucial for moving troops round Afghanistan.

"The Government must explain why our armed forces are having to do so much with so little. If we cannot move our forces by air they are more vulnerable on the ground. How on earth did we get into such an unacceptable position?"

Labour MPs accused Tories of playing politics with the helicopter issue.

Former defence minister Peter Kilfoyle said: "David Cameron and Liam Fox are wrong to be touring the TV studios attacking us over helicopters when what the men on the ground are saying is that 'helicopters are not the answer to any problems'.

"The last thing that our troops and their families want to hear is politicians trying to find some callous advantage from what will continue to be a tough but crucial battle in Afghanistan."

Former foreign secretary Lord Owen called for former defence secretary and Nato secretary general Lord Robertson to be recalled to Government to take charge of policy on Afghanistan and Pakistan.

He said it was "unprecedented and deplorable" that, according to a leaked Government paper, defence secretary Bob Ainsworth was 21st out of 23 in the Cabinet hierarchy.

Liberal Democrat leader Nick Clegg said it was now clear that Britain had overreached itself in trying to import a western-style liberal democracy in Afghanistan.

"Does the Prime Minister now accept that, at best, what we can do is stabilise Afghanistan, to provide a space for the state to grow?," asked Mr Clegg.

"And so does he see that, since our troops first stepped into Afghanistan, the Government strategy has been over-ambitious in aim and under-resourced in practice?

"Isn't it time to commit the necessary resources, and set a reasonable goal? When exactly will the Prime Minister find a way to send the desperately-needed helicopters to our troops on the ground? And when will he seek full co-ordination of the international political strategy in Afghanistan?"