Pressure intensified on the UK Government last night as the families of the Nimrod crash victims demanded evidence that the RAF's remaining fleet of 15 aircraft are safe to fly.

Shona Beattie, the widow of Flight Sergeant Stephen Beattie, from Ardler, near Blairgowrie, led the protests as she attacked the MoD for refusing to accept a coroner's judgment that the aircraft should be grounded.

Mrs Beattie's husband was among 14 servicemen - 10 of whom were based at RAF Kinloss in Moray - who died after a Nimrod MR2 exploded when a fuel leak occurred following air-to-air refuelling over Afghanistan two years ago.

At the conclusion of a two-week inquest into the deaths, Andrew Walker, assistant deputy coroner for Oxford, said that Nimrod aircraft had suffered a design flaw since they came into service almost 40 years ago and had never been airworthy.

However, Bob Ainsworth, the Armed Forces Minister, rejected Mr Walker's ruling and insisted that the RAF's Nimrods remained safe to fly.

There were also claims yesterday that at least 10 aircrew at RAF Kinloss have left their jobs amid fears over the safety of the ageing Nimrod fleet. Mrs Beattie, speaking in a BBC radio interview yesterday, stepped up pressure on Des Browne, the Defence Secretary, by arguing that the MoD's approach was endangering more lives.

“We got the verdict on Friday, but the MoD's reaction has not helped us to get closure,” she said. “It is making a mockery of the judicial process.

“I can't understand why it would not be a good thing to make the aircraft ALARP [reducing risk to As Low As Reasonably Practicable] as soon as possible for our friends that still fly them.”

She added that if the MoD was sure that the Nimrod was fit to fly, it should publish proof.

“If they are so confident, why did they not produce this in court in the past weeks?” she said. “Let us see the evidence and we will be happy. It would be fantastic if we could see it in black and white.”

Graeme Knight, father of Sergeant Ben Knight, who also died in the crash, told the BBC that he had harboured fears long before the crash about the fleet after some of his son’s trips were cancelled over safety concerns.

“We used to argue on a regular basis. I used to ask, ‘Is it safe?’, and he kept reassuring me it was. Unfortunately I was proved to be right and he was proved to be wrong.”

Mr Knight said he wanted the RAF to comply with the coroner’s wishes and make the fleet airworthy as a matter of urgency. He added that he would not stop campaigning for justice over the deaths until someone was held responsible. “As far as I am concerned the RAF killed my son and retribution needs to follow,” he said.

The comments from the victims’ families came as claims emerged that at least 10 Nimrod pilots and aircrew have quit their posts at RAF Kinloss in the last decade because of safety concerns.

David Morgan, an aviation expert, said that he was aware of a number of Nimrod personnel who had left the Scottish air base following worries about the aircraft’s systems, including air-to-air refuelling.

Mr Morgan, who has flown with Nimrod crews over the last 20 years, said: “I know of at least 10 aircrew who left because they were getting worried about the maintenance level of the Nimrod and its reliability.”

He described air-to-air refuelling as “dangerous” and claimed crews had become increasingly anxious as the aircraft began showing problems in their hydraulic, electrical and fuel systems due to their age.

Bob Hellyer, a retired squadron leader and former Nimrod pilot who was based at RAF Kinloss, also criticised the RAF’s use of air-to-air refuelling.

He said that the system, which was introduced during the Falklands War, should have been stopped when that conflict came to an end, as it was no longer necessary.

The MoD said it would not comment on Mr Morgan’s claims.

However, in a statement Air Marshal Sir Barry Thornton, the RAF’s most senior engineer, said: “We have stopped air-to-air refuelling and no longer use the very hot air systems in flight. This eradicates any dangers from the serious design failures noted by the coroner that have been present in this aircraft since the 1980s.

“These measures have been supplemented with enhanced aircraft maintenance and inspection procedures to ensure the aircraft, as it is today, is safe to fly.”

He added: “The Ministry of Defence and the Royal Air Force place the highest priority on airworthiness and the safety of our personnel in the air . . . we would not ask our personnel to fly in aircraft we did not believe were safe.”