Doctors are preparing to challenge the Government's decision not to order an inquest into the death of weapons expert Dr David Kelly.
In June, Attorney General Dominic Grieve ruled out the option and told MPs the evidence that Dr Kelly took his own life was "overwhelming".
But a group of doctors later accused the Government of being "complicit in a determined and concerted cover-up", saying they would seek a judicial review of Mr Grieve's decision.
They must now raise substantial funds to mount a legal challenge in court.
Dr David Halpin, a former orthopaedic surgeon who has campaigned extensively for a "proper investigation" of Dr Kelly's death, said "hundreds of questions" remain unanswered.
"The country is mired in mendacity and the only way you can deal with the mendacity is to challenge it and expose it," he said.
"Many questions have gone unanswered and many answers have gone unquestioned.
"Why has Dr Kelly not had an inquest? We have to get one and we are extremely determined - we regard it as a most important case. But this does hinge on public support."
The group needs to raise £50,000 to cover initial legal fees and lawyers must be instructed by August 30. This is to enable proceedings to begin by September 8, the legal deadline for launching a judicial review, Dr Halpin said.
Dr Kelly's body was found in woods close to his Oxfordshire home in 2003, shortly after he was revealed as the source of a BBC report questioning the accuracy of a government dossier arguing the case for war in Iraq.
