The families of 14 servicemen killed in an RAF Nimrod surveillance aircraft that exploded over Afghanistan after a fuel leak reacted with fury yesterday when the Government rejected a coroner’s judgment that the whole fleet should be grounded.

Andy Knight, the brother of Sergeant Ben Knight, one of the victims, said that the decision was “an insult to all the families”. Richard Mitchelmore, the father of Flight Lieutenant Leigh Mitchelmore, added: “The Ministry of Defence is going to do absolutely nothing. These planes will still be flying and these boys will risk their lives every day.”

The call to ground all 15 RAF Nimrod MR2s came from Andrew Walker, assistant deputy coroner for Oxford, at the conclusion of a two-week inquest into the 14 deaths.

He said that the Nimrod, known as XV230, which exploded after a raging fire on board at 3,000ft over southern Afghanistan in September 2006, was unsafe to fly. All the Nimrods, he said, had suffered from a basic design fault from the moment they came into service nearly 40 years ago. Since then the fleet has completed hundreds of thousands of flying hours.

“I have no doubt that these fine men will never be forgotten and their loss will be keenly felt by their families, friends and our Armed Forces,” Mr Walker said. “The aircraft was, in my judgment, never airworthy, from the first release to service in 1969 to the point where the Nimrod XV230 was lost.”

Chris Yates, an aviation expert at Jane’s Information Group, told The Times: “If this was a civilian airliner, there is no question that all similar aircraft would have been grounded. But the military work in different ways because they are operating in warzones and the same rules don’t apply.”

Under the Corporate Manslaughter and Corporate Homicide Act 2007, the MoD could be liable to prosecution in any future incident of this kind, but is exempt from any charge for the Nimrod crash because the legislation is not retrospective.

Mr Walker’s condemnation of the Nimrod was his first serious foray against the MoD since Des Browne, the Defence Secretary, went to the High Court in March to try to win an order for the Oxford Coroner to temper his critical language.

Mr Walker said that the doomed Nimrod with 12 RAF servicemen from 120 Squadron based at RAF Kinloss, one member of The Parachute Regiment and one Royal Marine on board, had a “serious design flaw” that was discovered by neither the manufacturers nor by those entrusted with maintaining the ageing aircraft. The inquest at Oxford Assizes was told that fuel had leaked into No 7 dry bay shortly after the aircraft completed air-to-air refuelling, which had ignited on contact with a hot-air pipe that was uninsulated, despite generating temperatures of up to 500C (932F).

Mr Browne offered his profuse apologies to the families of the victims when the RAF board of inquiry into the tragedy was published in December. Yesterday the MoD confirmed that it was now waiting for lawyers acting for the families to detail compensation claims, which are expected to run into millions of pounds. The MoD has promised to meet the claims as quickly as possible.

Bob Ainsworth, the Armed Forces Minister, rejected the Coroner’s demand for the Nimrods to be grounded, and insisted that they were safe to fly. “My thoughts are with the families, friends and colleagues of those who died in XV230. On behalf of the MoD and the RAF, I would like to apologise again to the families of those who died for our failings which led to this tragic incident,” he said.

He added that Air Chief Marshal Sir Glenn Torpy, Chief of the Air Staff, had reaffirmed that the Nimrod was airworthy “and that we are dealing with all the issues raised by this incident”.

“The Nimrod is saving lives in operational theatres every day,” Mr Ainsworth said. “However, if it was not safe we would not be flying it. It is safe with the measures we have taken and that is why we will not be grounding the fleet.”

His statement was backed up by Air Chief Marshal Sir Barry Thornton, the RAF’s most senior engineer, who 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.”

Sir Barry said that the design flaws had been present since the 1980s, not 1969, as the coroner had said. The RAF’s top engineer insisted that the Nimrods could be flown safely until their planned retirement from service.

However, Mr Walker, who recorded narrative verdicts in the case of the victims, said there had been “a cavalier approach to safety”.

“It seems to me that this is a case where I would be failing in my duty if I didn’t report action to the relevant authority that would prevent future fatalities. I have given the matter considerable thought and I see no alternative but to report to the Secretary of State that the Nimrod fleet should not fly until the ALARP [as low as reasonably practicable] standards are met.”

Two Nimrod safety reviews are still being carried out, which could lead to the MoD having to revise its decision. Charles Haddon-Cave, QC, was commissioned by the MoD to examine arrangements “for assuring the air-worthiness and safe operations of the Nimrod MR2” in the period leading up to the accident in 2006.

In the second review, the defence company QinetiQ is looking into the safety of the fuel system and has published an interim report.

40 years of service

— One of the Nimrod pilots, aged 39, had completed 3,800 flying hours on the aircraft. The Nimrods, since coming into service nearly 40 years ago, must have flown several hundred thousand hours

— Air-to-air refuelling on Nimrods remains suspended

— Original design was based on the de Havilland Comet, the first commercial jet airliner

— In the early 1980s it was upgraded to an MR2 version, with its main roles being sea surveillance, anti-submarine warfare and search and rescue. In the Cold War it hunted Soviet submarines

— The Nimrod served in the 1991 Gulf War and the 2003 invasion of Iraq

— Without refuelling it can remain airborne for ten hours with a top speed of 575mph

— It has a crew of 13

— All Nimrods were grounded temporarily in February last year after a safety check uncovered a dent in a fuel pipe

— The voice recorder on the doomed aircraft included the warning “Fire in the bay”

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