Britain’s Cold War Armed Forces were so run down by the end of the 1970s that they would have been overwhelmed in the event of a Russian attack, according to secret files made public today.

Papers released by the National Archives at Kew, west London, under the 30-year rule, reveal that RAF Phantom jets had enough ammunition for just two days’ fighting, air defence missile batteries could only be fired twice, and the Navy could not match the Soviet submarine threat.

The Army, meanwhile, would be so stretched that, even when fully mobilised it would be unable to cope with the expected widescale campaign of sabotage and subversion by the Soviet special forces.

A shocked Prime Minister James Callaghan described the situation as a “scandal” when he learnt how far the forces had been depleted, and called for heads to roll.

“Heaven help us if there is a war!” he scrawled in one hand-written note.

But with money tight, ministers had to accept that there was little they could do until new equipment like the Tornado jet fighter became available in the mid-1980s.

The scale of problem became apparent after the Joint Intelligence Committee (JIC) – the UK’s senior intelligence body – warned in late 1977 that, in the event of a conventional war, the Russians could unleash up to 200 bombers and 18 submarines against the UK.

In addition, the Russians were expected to mine Britain’s coastal waters while landing special forces troops from the Soviet diversionary brigades – disguised as civilians or Nato soldiers – to sabotage key targets.

“UK forces cannot match the threat postulated by the JIC assessment,” the Chiefs of Staff noted in January 1978.

“Air defences would be outweighed because aircraft would be outnumbered and stocks of air defence munitions would sustain operations for only two or three days.

“Maritime forces need better anti-submarine weapons, and face a massive threat from submarine and air-launched missiles and also from mines; the most serious deficiency is in numbers.

“The Army in the UK would, until mobilisation is complete, have insufficient forces to meet its commitments; after mobilisation of the reserves, a process taking between 15-20 days, the Army would be able to counter the currently assessed Soviet land threat during the initial stages of the war but, lacking supporting arms and logistic support, it would be inadequate to deal with any more significant threat, including sabotage or subversion on a wide scale.”

The chiefs went on to warn that much of the military command and control system was “unhardened, insecure and vulnerable to sabotage and jamming” while the Bloodhound surface-to-air missiles protecting key bases had only enough ammunition for a single re-load.

Royal Navy minesweepers, meanwhile, would be tied up keeping open the sea lanes to the nuclear submarine base at Faslane and would be unable to clear the routes across the English Channel.

If the Russians chose to use their large arsenal of chemical weapons, British forces would be vulnerable as, while most troops had respirators, only a few had the necessary protective clothing as well.