Britain announced Tuesday it will shrink its armed forces and scrap key assets like its flagship aircraft carrier, in a defence review that forms part of stinging cuts across the whole public sector.

Prime Minister David Cameron said 17,000 service personnel would go from the British Army, Royal Air Force and Royal Navy by 2015 -- but vowed there would be "no cut whatsoever" to the level of support for forces in Afghanistan.

As part of eight percent cuts to the 37 billion pound (42 billion euro, 58 billion dollar) Ministry of Defence (MoD) budget, the Royal Navy's flagship HMS Ark Royal aircraft carrier is also being scrapped immediately along with Britain's fleet of Harrier jets.

And although the government will retain its nuclear deterrent, a decision on renewing the system will be delayed until 2016 to save money.

The changes in the defence review suggest that in the long-term, Britain could not engage in wars such as those in Iraq and Afghanistan.

It assumes the armed forces will only be equipped to send 6,500 troops for a long-term operation and a maximum of 30,000 troops for a short-term conflict.

Speaking to a packed House of Commons, Cameron said his government had inherited a 38-billion-pound "black hole" in the defence budget when it took power in May and warned: "We cannot go on like this.

"Britain has traditionally punched above its weight in the world and we should have no less ambition for our country in the decades to come.

"But we need to be more thoughtful, more strategic, and more coordinated in the way we advance our interests and protect our national security and that is what this review sets out to achieve."

The announcements came ahead of sweeping cuts of up to 25 percent in most government departments which will be unveiled Wednesday, as Cameron's coalition battles to cut public sector borrowing from 149 billion pounds to 20 billion pounds by 2015-16.

Army personnel will be cut by 7,000 to 95,500, the navy will fall 5,000 to 30,000 and the Royal Air Force will decrease by 5,000 to 33,000, while 25,000 MoD civil service jobs will go.

The government is also bringing all Britain's 20,000 troops back from Germany by 2020, saying the bases are a relic of the Cold War.

The leader of the opposition Labour party, Ed Miliband, described the review as "hastily prepared" and "simply not credible", while members of Cameron's Conservative party have also complained they go too far.

But the head of Britain's armed forces, Jock Stirrup, said that while the cuts were far from ideal, they were necessary given the country's economic situation.

"Of course we would rather have sustained (previous) capability all the way through," he told the BBC.

"But you have to make difficult choices when you're in these sorts of financial circumstances and our focus has to be on Afghanistan."

Cameron insisted Britain's defence budget would remain the fourth largest in the world and would meet NATO's target for members to spend more than two percent of GDP on defence.

There were also announcements of fresh spending in the review, the first of its kind for 12 years.

Cameron notably promised 650 million pounds over the next four years for a national cyber security programme, highlighted in Monday's new national security strategy as a "tier one" threat.

The decision to axe Ark Royal earlier than the 2014 date originally planned will leave Britain without an aircraft carrier capable of launching jets for around a decade.

It will be 2020 before two new aircraft carriers -- ordered in part because it would be more expensive to scrap pre-agreed contracts -- can be used for this purpose.

Britain has 10,000 troops in Afghanistan, making it the second biggest contributor of foreign forces after the United States.

The White House said Tuesday it believed Britain would still have a "first-rate military" despite the cuts.

"Our view is that certainly the level of help and cooperation that we get and the sacrifice of that country in places like Afghanistan certainly is vital and important to our coalition," White House spokesman Robert Gibbs said.