Carrier built for only three years in service

• An artist's impression of one of the new carriers

The government's strategic defence and security review, to be published today, will show that the first of the two vessels, the Queen Elizabeth, which is meant to have a 40-year lifespan, will only sail until 2019, probably without having carried any aircraft other than helicopters, sparking speculation last night that it will be sold.

An MoD briefing has shown that although the 5.2 billion carriers project has been saved, Britain's military capability will be dramatically reduced over the next two years as the Treasury exacts cuts from the military budget.

While the decisions will safeguard 10,000 jobs on the Clyde and in Rosyth, and possibly the future of Scottish ship-building, the vessels will not be what the navy and RAF had hoped for.

Meanwhile, a reduction in the number of strike fighter jets and a postponement in bringing them into service is bad news for RAF Lossiemouth in Moray, which is under threat and could be closed or mothballed until 2020.

The last of the current crop of carriers, the Ark Royal, is to be axed with immediate effect, meaning the navy will be without a major carrier until HMS Queen Elizabeth sets sail as a helicopter platform by 2016.

More: Defence cuts

• Tim Ripley: Different review, same conclusions

• Outlook for Scottish bases still unclear

• Scotland's role in the four core threats

• Timeline

Only in 2020, a year after it is brought into service, will the second super carrier, the Prince of Wales, be given the new joint strike fighters. But MoD sources have revealed that the fighters are to be scaled down and there will be fewer than first planned. The catapult launch system on the carrier will be changed to allow it to be used by French and Americans forces.

The government is also expected to confirm that the renewal of the Trident nuclear deterrent will be delayed beyond the present timescale of the end of 2014.

The revelations appear to confirm fears expressed by US secretary of state Hillary Clinton last week about a substantial reduction in the UK's military strength. Prime Minister David Cameron sought to reassure the US last night, telling President Barack Obama that the UK would remain a "first-rate military power and a robust ally".

In a phone call to the White House, the Prime Minister insisted that Britain "remained committed to meeting our responsibilities" in Nato.

A Downing Street spokeswoman said: "The Prime Minister said that the UK would remain a first-rate military power and a robust ally of the United States.

"We would be reforming our defence and security capabilities for the challenges of the 21st century. We remained committed to meeting our responsibilities in Nato and would continue to work closely with the US on the full range of current security priorities."

At the weekend, Chancellor George Osborne was barely able to hide his anger that the carriers had been allowed to go ahead, following a concerted campaign by Defence Secretary Liam Fox, supported by Business Secretary Vince Cable. And last night, opposition parties attacked the decision to downgrade the navy and warned of the consequences to Britain's global standing.

Labour MP Ian Davidson, who represents Glasgow South West, said: "I have always believed in aircraft carriers so Britain can project power and influence around the world.

"The clue is in the name. Considering not flying planes off them is incompetence and mismanagement on a grand scale."

He went on: "The defence select committee warned that the rushed nature of this review would lead to mistakes, some of them serious.

"It would be totally wrong for Britain to lose all our ability to project airpower in support of troops, wherever in the world we need to deploy them."

The revelations came shortly after the government published the first of its papers covering the future of defence and security in the UK.

The document, which concentrated on strategy and risk, as opposed to the personnel and equipment issues to be outlined into today's paper, identified a league table of the most important threats facing the UK.

The government said its greatest concerns were a possible terrorist attack using chemical, biological, radiological or nuclear weapons and cyber attacks. The report also raised the prospect of an attack using artificial intelligence.

At the briefing yesterday, government officials warned cyber attacks could be the biggest potential threat of them all and raised the possibility of passenger planes "dropping out of the sky" or of Britain's communications being brought down.

The recent cyber attack on Iran to target its nuclear programme was highlighted, as was an attack on Estonia that brought the country to a halt. Officials said cyber attacks were an issue for the 2012 Olympics in London – the 2008 Games in Beijing were subjected to some 12 million cyber attacks a day.

The government also put into its top tier of threats an attack on mainland Britain by Northern Irish terrorists, the first time such a possibility has been high on the agenda since the peace process ended.

The other two tier-one concerns were a natural disaster, such as a flu pandemic or flooding, and an attack on allies of Britain in Nato or the European Union. Government sources said it was this last threat which had kept the carriers in their plans, because Britain would need their capabilities in future. The prospect of a nuclear attack from a foreign state was only in tier two.

The SNP's Westminster leader and defence spokesman Angus Robertson MP said: "The acknowledgement that the equipment we have available is still too rooted in the Cold War mind-set does make it absolutely extraordinary that renewal of Trident has been excluded from this review process – that makes absolutely no sense at all."

A fresh attack on the Falkland Islands in the South Atlantic was relegated to a tier-three threat. However, officials stressed this reflected their belief as to how likely an attack was, and they insisted all the threats in the three tiers were considered "equally important".

Foreign Secretary William Hague said: "Under this government, there is a proper mechanism for the bringing together of strategic decisions about our security, defence, diplomacy and development, after years of ad-hoc thinking and poor decision-making. This week, we will present the new national security strategy and the results of the strategic defence and security review.

"After the drift of the last decade, this country will finally have a clear vision of how to build up Britain's influence in the world and protect our security."