Exclusive: MoD spending crisis means planes could be rushed out of service, rather than phased out over several years

The RAF's entire fleet of Tornado ground attack aircraft could be rushed out of service because of a fresh spending crisis at the Ministry of Defence, the Guardian has learned.

With the department trying to find an extra £1bn savings before the end of the spending round next month, ministers and senior military officials have been presented with a range of unpalatable options.

One involves the immediate withdrawal of the RAF's eight Tornado fighters in Afghanistan, followed by an accelerated withdrawal of the rest of the fleet from service, possibly within three years. Other options include axing thousands more soldiers from non-combat units in the army, or withdrawing more ships from the Royal Navy's already diminished fleet.

"It's a complete mess," said one Whitehall source. "The government wants the military to play a role on the global stage, but the MoD is running out of money to meet its commitments." Any withdrawal from the mission in Afghanistan would cause uproar, but the Tornados are vulnerable because there are only a few of them there, and they could be deemed non-essential: it would still leave more than 100 fast jets from other countries.

Under last year's strategic defence and security review (SDSR), the RAF's 100 or so Tornados were due to be phased out over several years, with the RAF still having a rump of 18 by 2015.

But decommissioning all of them, and more quickly, is now considered a possibility. Under this scenario, the MoD would try to accelerate into service more Typhoon aircraft, the Tornados' long-term replacement. This option may have become more attractive because the MoD is no longer expecting to sell some of its Typhoons to Oman in a £600m deal.

Professor Malcolm Chalmers, a defence expert at the Royal United Services Institute (RUSI), said: "If all the Tornados are withdrawn from service before 2015, it will be further evidence of just how difficult a task balancing the MoD's books is proving to be. It would be a significant further capability cut in addition to those announced in the SDSR. It is unlikely to be the last as the MoD struggles to meet the savings target it has been set."

He added: "The MoD is consciously choosing to allow gaps in medium-term capabilities – such as carriers and now fast jets – to develop so that it can focus its limited resources on Afghanistan … and on long-term investment programmes. Yet this strategy is predicated on the assumption that, post-2015, the cuts in the MoD will be quickly reversed. If this does not happen future defence reviews will have no other choice than to turn temporary capability gaps into permanent ones."

The scramble to identify cuts has come about because the MoD underestimated the cost of commitments made at the time of the SDSR, which was published last October. For months before the review, the MoD had been expecting to make cuts based on an overall budget reduced by 4%. But with days to go before the review was due to be finalised, defence officials realised the Treasury wanted cuts of 8-10%.

"It was done far too quickly. The MoD tried to do a new defence review in days. It was a farce," said a source.

The defence secretary, Liam Fox, now needs to sign off new cost cuts by the end of March unless the Treasury softens its hardline stance. One option could even see the Treasury making a loan to the MoD to help it through the next year or two.

Earlier this month the Guardian revealed that the Royal Navy would no longer be sending a warship to patrol the Caribbean, where it has played an active role in counter-narcotic and disaster relief operations.

Twelve Chinook helicopters which were promised by the government in the autumn's defence review may also become casualties of the cuts. Peter Luff, the defence procurement minister, has said the contract is "subject to negotiation".

The MoD refused to be drawn on the discussions about cuts. A spokesman said: "A number of different options are being considered. We cannot say with any clarity what those decisions will be. No decisions have been taken yet."

BAE Systems, which part-builds and has a support and maintenance contract for the UK's Typhoons, also refused to be drawn, particularly over any deal with Oman. "That is a matter for the Ministry of Defence," a spokesman said.

Before the SDSR, all three services fought bitterly to protect their own personnel and forces, with the Navy and the RAF bearing the brunt of the cuts. The RAF is likely to be furious if the Tornado is sacrificed as part of the spending round.

The RAF now has 71 Typhoon aircraft, which were delivered in two tranches. It has been reported that the first tranche of 48 could already be obsolete by 2015.

In 2009 the RAF ordered and is awaiting delivery of another 40 of the more modern tranche 3 Typhoons.

It is envisaged that the Typhoon and the Joint Strike Fighter, currently under development, will be the RAF's main attack aircraft from 2020.