Former defence procurement minister Lord Drayson must attend the inquest of 10 British servicemen, including one from Hampshire, killed when their Hercules aircraft was shot down in Iraq to explain why the craft lacked a vital safety feature, a lawyer said today.

The lawyer for two of the dead men's families said he wants Lord Drayson to explain "budgetary constraints" which led to modifications to stop RAF Hercules' fuel tanks exploding not being installed until after the tragedy on January 30 2005.

On that day small arms fire by insurgents pierced a fuel tank on the Hercules C130k, causing it to explode and blow off a wing.

The inquest heard today that despite multiple written requests in the years before the crash for anti-explosive measures to be fitted to Hercules fuel tanks, the matter simply "dropped off the radar".

US Hercules have been fitted with such measures since the 1960s.

John Cooper, for the families of Sgt Bob O'Connor and Cpl David Williams, both killed, read today from a Parliamentary Defence Committee report made in May 2006 after the Hercules tragedy was mentioned in the Commons.

"The lifting of (Ministry of Defence) budgetary constraints would allow better self-protection of all aircraft," said Mr Cooper, quoting the report.

"It is widely acknowledged that ESF (explosive-suppressant foam) would have given the crew of XV179 (the plane's number) a much better chance of surviving the attack of January 2005."

Mr Cooper told the court: "We will be asking for Lord Drayson, the Procurement Minister at the time, to attend this inquest."

The retrospective fitting of Hercules aircraft with ESF, which stops fuel tanks exploding if hit by small arms fire, costs about £600,000 per plane.

An un-named RAF squadron leader who was the RAF's desk officer for the Hercules C130 fleet, told the inquest today he recalled being sent two letters in 2000 by a former Hercules commander - before and after he deployed to Sierra Leone - about the need for anti-explosive fuel tank protection.

The witness, referred to as DR, said he recalled meeting face-to-face with the officer who wrote the letters - but no action was taken.

DR said from behind a screen: "There were many priorities but this one actually just dropped off the radar as far as I can see."

Following the 9/11 terror attacks on New York in 2001, DR said he contributed to a 'wish list' with regard to fitting the RAF's Hercules fleet with the latest capabilities. ESF, or any comparable anti-explosive system, was not on that list, he said.

The matter of Hercules fuel tank protection was also raised in post-operational report by RAF Lyneham-based 47 Squadron following its deployment to Afghanistan 2002, the court heard. But ESF was not mentioned as a requirement for Hercules in an upgrade of the fleet that same year, DR said.

The fitting of ESF to RAF Hercules began only after the 2005 tragedy. Up to 30 of the RAF's 44 craft have since been fitted.

Wiltshire Coroner David Masters expressed astonishment that a matter raised by a Hercules commander in 2000 could "drop off the radar" in the way described.

DR said this Hercules commander retired in the months after voicing his concerns, which meant the matter fell off the RAF's "corporate memory" - a common problem in the Armed Forces as personnel move from post to post.

Mr Masters, stating this was a matter in need of urgent address, said: "I am a coroner and I shall retire one day and someone will succeed me. I pursued matters raised by my predecessor and I would hope my successor would pursue matters I have raised. That's how it should work."

The victims based at RAF Lyneham in Wiltshire were: RAF 47 Squadron's Flt Lt David Stead, the pilot, 35; Flt Lt Andrew Smith, 25, the co-pilot; Master Engineer Gary Nicholson, 42; Flt Sgt Mark Gibson, 34, Australian airman Flt Lt Paul Pardoel, 35, a navigator; and from Lyneham's Engineering Wing, Chief Technician Richard Brown, 40, an avionics specialist; Sergeant Robert O'Connor, 38, an engineering technician; and Corporal David Williams, 37, a survival equipment fitter, a passenger.

Acting L/Cpl Steven Jones, 25, of Fareham, a Royal Signals soldier, was also part of the crew.

Sqn Ldr Patrick Marshall, 39, from Strike Command Headquarters, RAF High Wycombe, was another passenger on the Hercules.