The Government's defence review was a cash-driven exercise which will diminish Britain's influence in the world, the former head of the armed forces said today.
Air Chief Marshal Lord Stirrup, who was chief of the defence staff at the time of last year's Strategic Defence and Security Review (SDSR), said the overriding requirement had been to cut costs.
Giving evidence to the Commons Defence Committee, Lord Stirrup said that the UK now faced a period of "strategic shrinkage" as a result of the swingeing cuts to the military.
"Although people have charged that the Strategic Defence and Security Review was not strategic, it most certainly was strategic - but the strategy was to eliminate the deficit," he said.
"In all of our considerations the requirement to do that - and therefore the requirement to reduce expenditure - overrode just about everything else."
While Lord Stirrup said he believed action had been necessary to rebuild the public finances, it meant Britain had little in reserve to deal with unforeseen threats such as an attack from Iran.
His comments came the day after David Cameron dismissed claims by the individual heads of the Army, Royal Navy and RAF that Britain no longer aspired to the "full spectrum" of military capabilities.
Lord Stirrup said that the decision to axe the Nimrod MR4A maritime patrol aircraft meant that Britain would not be able on its own to put a naval taskforce to sea if there was any threat of a submarine attack.
"I along with others made it quite clear that if we went ahead with the decision to get rid of maritime patrol aircraft, in circumstances of a resurgent submarine threat we would not be able to send a naval taskforce to sea unless somebody else provided that capability," he said.
He dismissed a claim in the national security strategy document which accompanied the SDSR that the British national interest "requires us to reject any notion of the shrinkage of our influence".
"That particular sentence was debated, as you can imagine, quite a lot," Lord Stirrup said.
"Personally, I didn't buy it. My personal view is that if the priority is to eliminate the deficit over the course of the parliament, then the rather drastic action that will be necessary will mean a period of strategic shrinkage."
Lord Stirrup expressed concern that the concentration of the remaining military resources on current operations could leave Britain exposed if other unforeseen threats did emerge.
"We do need to keep something in reserve to deal with such very serious threats should they materialise," he said.
He cited the possibility of an attack by the Iranians on British interests in strategically vital shipping routes in retaliation for an attack by another country on their nuclear facilities.
"They could do things, in regards for example to the Straits of Hormuz, which we would regard as a casus belli. We could could not fail to respond to them because the consequences to this country would be so dire," he said.
He also warned that plans to rebuild the armed forces after 2015 depended upon the economy growing very much faster than it is at present.
"All of this depends upon real terms growth in the second half of the decade - and meaningful real terms growth. I don't mean 0.2%-a-year in real terms, I mean something substantially more than that," he said.
"It is still very much an area of uncertainty."