The maintenance work is expected to take about 10 months

The MoD said HMS Torbay would go to Faslane's Babcock Naval Services on the Clyde for a Revalidation Assisted Maintenance Period (RAMP) in 2007.

Dockyard company DML said it had been expecting to get the work under the terms of an existing agreement.

It added that the move would not affect jobs at the yard.

'Unique' yard

DML said it hoped the move would be a one-off, but it would still have some involvement in planning the work.

It added that it would seek financial recompense from the MoD.

The upgrade and maintenance is expected to take about 10 months to complete.

Plymouth Devonport MP Alison Seabeck said the contract loss was disappointing, but not did not spell the end for the yard.

She said: "It is a competitive tendering process and, for whatever reason, the tender was not as competitive as Faslane. It is a blow."

She added that she and Plymouth Sutton MP Linda Gilroy had met with Defence Procurement Minister Lord Grayson recently and that all three agreed the yard would continue.

Ms Seabeck said: "He said it is quite clear that Devonport has a future. It is unique, and there is nowhere else in the UK that can provide the services that it provides."