The crash claimed the lives of 29 people

He said: "It does seem to me on first reading that it is covering the same ground with the same information. There is no new evidence and no new facts," he said.

The Ministry of Defence made a limited comment on the findings. A spokesman said: "It is a complex issue and we will study the report in detail and make a response."

The pilots - Jonathan Tapper, 30, from Burnham Thorpe in Norfolk, and Richard Cook, 28, from Church Crookham, Hants - died when the helicopter crashed in thick fog on its way from Northern Ireland to Inverness in June 1994.

All 29 people on board were killed, among them 25 senior Northern Ireland intelligence officers, who were travelling to an army base for a special meeting.

The inquiry followed a campaign to clear the names of the pilots who had been accused of "gross negligence" by senior RAF officers.

'Absolutely no doubt'

The all-party select committee of five peers, which has heard evidence for six months, cast doubt on the findings of the RAF air marshals.

The committee report said: "We unanimously conclude that the reviewing officers were not justified in finding that negligence on the part of the pilots caused the aircraft to crash."

They said their conclusion was based on all the evidence before them and the fact that the standard of proof required for blaming a pilot should leave "absolutely no doubt whatsoever".

The news has been welcomed by the families of the pilots, who are expected to appear at a press conference on Tuesday afternoon.

Flt Lt Cook's father John Cook had said he feared his son's name would not be cleared by the report.

The crash was one of the RAF's worst peace-time accidents.

The reviewing officers were not justified in finding that negligence on the part of the pilots caused the aircraft to crash.

Lords Select Committee report

It happened during a flight from RAF Aldergrove in Northern Ireland to Fort George, near Inverness.

The RAF's own internal inquiry originally ruled that it was impossible to establish the exact cause - but said there were no "human failings".

That conclusion was overturned by two senior RAF officers, Air Vice Marshal John Day and Air Chief Marshal Sir William Wratten - who reached a verdict of gross negligence.

But a fatal accident inquiry in Paisley, outside Glasgow, held that the cause of the accident was a mystery, and concluded that the RAF investigation was flawed.

The families had pushed for a new inquiry

But a succession of defence ministers have refused - including former Scottish Secretary John Reid - despite a series of allegations about the safety and reliability of the Fadec (Full Authority Digital Engine Control) engine software on board the Chinook fleet at the time of the accident.

The peers heard evidence that the engines were prone to massively speeding up or slowing down the rotors for no reason, and leaving no physical or electronic trace.

But the committee also heard from the RAF air chief marshals, who insisted that they were right to conclude that "gross negligence" was the cause of the crash.