The Defence Secretary has been accused of misleading Parliament over the capture of 15 British sailors and Marines in the Gulf last spring as it emerged that Iran has kept £1 million of seized military equipment.

The Conservatives said that Des Browne was “less than frank” after The Times disclosed Ministry of Defence papers showing that the Britons were seized in disputed waters, not Iraqi territory.

The MoD also rejected an application under the Freedom of Information Act to provide details of the location.

Mr Browne has told the Commons repeatedly that the patrolling Britons, who were held for a fortnight and paraded on Iranian television, were seized boarding a vessel in “Iraqi waters”.

An internal MoD paper released to The Times blames the incident on the lack of an agreed border in the waters between Iraq and Iran.

The seizure occurred, the top-level document states, because the US-led coalition created a notional sea boundary but omitted to tell the Iranians where it was. Revolutionary Guard patrol boats were crossing this line three times a week, the partially censored document shows.

The MoD has always insisted that the Britons were 1.7 nautical miles on the Iraqi side of that boundary. However, last summer The Times requested information “concerning the location and position of the search party”. Specifically, the request was for information from a technical device that communicated the boarding party’s position to the mother ship, HMS Cornwall.

In the past week the MoD gave its final response to this request: no information is being released because it would disclose operational tactics, routines and capability.

In a letter to The Times today Air Vice-Marshal Chris Nickols, assistant chief of defence (operations), said the MoD had been able to “demonstrate overwhelmingly” that the co-ordinates cited were correct.

“Our disagreement was instead about precisely where our personnel were detained,” he wrote.

“Even the Iranians never disputed that the co-ordinates given by the UK were firmly inside Iraqi territorial waters. That is why they were instead compelled to make up alternate co-ordinates for the incident.”

Liam Fox, the Shadow Defence Secretary, whose office saw the material released to The Times, said: “This in no way excuses the illegal actions by the Iranians. However, it seems that the MoD was less than frank in the details surrounding this dreadful incident. In light of this we will want to examine the words of the Secretary of State to Parliament to see if they were misleading or whether the Secretary of State was misled over what was a national humiliation.”

A source close to the Defence Secretary rejected Dr Fox’s statement, saying: “We didn’t mislead the House. We said they were picked up in Iraqi waters and we stand by that.”

Parliamentary questions by Dr Fox and other MPs have disclosed that the Iranians are still holding £1 million of British equipment. Some of it comes from a seizure of British servicemen patrolling the Shatt al-Arab waterway in 2004. They were accused by Iran of crossing to its side but were later released.

David Heathcoat-Amory, a former Foreign Office minister, called last night for a Commons defence committee inquiry into the fiasco to be reopened.

“I am going to be examining the report with a view to reopening it or at least getting clarification about why the Defence Secretary was giving categoric statements to the House of Commons saying that these boats were indisputably in Iraqi waters,” he told Channel 4 News.

British bounty

From 2007 the Iranians have

— Two rigid hull inflatable boats
— Seven carbines and four rifles
— Ten pistols and ammunition
— Communications and navigation systems
— Body armour, helmets and goggles
— Camera equipment

From 2004 they are holding

— Two combat support boats
— Six rifles and sights
— Six pistols and ammunition
— Radios and navigation equipment
— Global positioning system
— Maritime charts

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