Fourteen servicemen died when a Nimrod spy plane exploded in mid-air in September 2006, minutes after undergoing air-to-air refuelling.

Assistant Deputy Coroner for Oxford Andrew Walker said the entire fleet, which is based at RAF Kinloss in Forres, Scotland, was "unsafe to fly". "The crew and passengers were not to know that this aircraft, like every other in the Nimrod fleet, was not airworthy," Mr Walker said. "What is more the aircraft was, in my judgment, never airworthy from the first release to service in 1969."

He made the recommendation to ground the fleet until a "serious design flaw" was rectified as he gave his verdict following a three-week inquest at Oxford's Old Assizes. Mr Walker also criticised the "cavalier approach to safety" and said opportunities to spot the danger were missed.

But Armed Forces Minister Bob Ainsworth has refused to agree to the coroner's recommendation.

The families of the 14 servicemen reacted with fury at the decision calling it an "insult".

The explosion was caused by fuel leaking into a dry bay and igniting on contact with a hot air pipe. Fuel couplings should not have been in the same compartment, the inquest was told.

The coroner recorded narrative verdicts following the three-week inquest at the city's Old Assizes and then called for the grounding of the entire fleet which he viewed as "unsafe to fly".

He said: "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 (risk is as low as reasonably practicable) standards are met."

However, following the verdicts Mr Ainsworth offered apologies to the family but refused to ground the Nimrod fleet. He said: "The Nimrod is saving lives in operational theatres every day. 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."