Campaigners claimed the crash was caused by mechanical faults
Campaigners seeking to clear the names of two dead RAF pilots blamed for a 1994 Chinook helicopter crash may seek a judicial review.
The MoD has confirmed that a verdict of gross negligence on the Mull of Kintyre crash would not be overturned.
The decision came after a year-long review prompted by campaigners who had handed a dossier to the MoD, which they said included new evidence.
They have claimed there were serious flaws in the helicopter.
The crash, 14 years ago, killed four special forces crew and 25 senior members of Northern Ireland's intelligence community.
Those on board were headed for Fort George, a military base near Inverness.
Flt Lt Tapper, 30, from Burnham Thorpe, Norfolk, and Flt Lt Cook, 28, from Church Crookham, Hampshire, were initially cleared of blame by an RAF board of inquiry.
It ruled it was impossible to establish the exact cause of the crash.
A fatal accident inquiry reached the same conclusion.
However, that conclusion was overturned by two senior RAF officers who said the pilots were guilty of gross negligence for flying too fast and too low in thick fog.
A year ago the former Defence Secretary Des Browne agreed to review the case, after campaigners obtained a previously unpublished memo, using freedom of information rules, which they claimed would clear the pilots.
Campaigners said they may now seek a judicial review in the courts.
Mike Tapper, the father of one of the pilots, said the secretary of state "did not seem to be able to override his officials".
He said: "The best thing that has come out of this has been the report by Michael Powers which once you've read it you have now doubt whatsoever that the pilots were not guilty of gross negligence.
"No-one has put forward a valid or indeed any reason why your son made the waypoint change to fly voluntarily straight into the mountain.
"We will never give up, but it's very hard to see how you can go ahead when there is what can only be described as an institutional blockage within the Ministry of Defence."
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