The Rivet Joint RC 1 has been out of action for five weeks after returning from the Middle East. It is the only one in the RAF fleet, although two more are on order.
The news comes after a new Ministry of Defence report laid bear the size of defence cuts for both the RAF and Royal Navy. In 2000, according to the report, the UK
had 17 fighter squadrons and three maritime patrol aircraft. Today it has just seven squadrons and no patrol aircraft to monitor Russian incursions into UK airspace and coastal waters.
Just last week RAF Typhoon fighters were scrambled after two Russian Bear bombers were spotted off the coast of Cornwall, and former head of the RAF Air Chief Marshal Sir MIcheal Graydon warned that Britain was “at the mercy” of Russian aircraft.
And Britain’s top commander in Nato, Gen Sir Adrian Bradshaw, warned that Russia’s threat could “slide into war”.
In 2011 the Government controversially scrapped a new fleet of Maritime Nimrod spy plane replacements, at a cost of £4bn, as part of savage cost cutting measures.
Though less sophisticated their cheaper replacement, the US-built Rivot Joint can still be used to detect vital information about Russian movements in the air and on the sea.
“The Rivot Joint is basically a mobile listening post, and it is able to listen in to transmissions in the air, ground or sea,” said Air Commodore Andrew Lambert, of the UK National Defence Association.
Last month, senior commanders were forced to ask the Americans and French to monitor a Russian submarine detected off the West coast of Scotland, after the UK had no assets to shadow the vessel.
An RAF source told the Sunday Express: "The fact is we cannot maintain constant airborne surveillance of the northern North Sea as we have done in the past,” said the source.
"Getting rid of the Nimrod sent a clear signal to Russia that we have no capability to monitor them"
The number of RAF fighter and bomber aircraft today stands are 149, compared with more than 400 in 2000 when, according to the report, the number of squadrons stood at 17.
And while the air force currently has 90 Typhoons, it lacks pilots.