DEFENCE Secretary John Hutton said lessons would have to be learnt 'pretty quickly' following the mid-Atlantic collision between British and French nuclear submarines.

HMS Vanguard, which was refitted at Devonport Dockyard, and French sub Le Triomphant – both believed to have been carrying nuclear warheads – were damaged in the crash earlier this month in the Atlantic.

Speaking in the House of Commons yesterday, Mr Hutton said: "The First Sea Lord has made clear there is a very careful investigation going on to explore exactly how this event happened and what conclusions we should draw from it.

"I don't want to pre-empt the First Sea Lord's inquiry but clearly if there are any lessons to be learnt, and I suspect there are, we need to learn them pretty quickly."

The collision is thought to have happened on February 3 or 4, when both submarines were submerged and on patrol.

Despite being equipped with sonar to detect other vessels, neither submarine's crew apparently realised the other vessel was in the same part of the ocean.

A senior Royal Navy source said the potential consequences of such a collision were 'unthinkable'.

Both vessels made their own way back to base, and on February 7 the French Navy published details of a collision. At the time, they thought their submarine had struck a sunken container.

In Britain, the Ministry of Defence initially refused to confirm the incident, saying it was not policy to comment on submarine operations, but on February 16 the Navy issued a statement saying the two vessels hit each other while travelling at very low speeds and no one was injured.

The MoD said the Vanguard returned to its base in Faslane, Scotland, with only 'scrapes'.