Devonport is the sole UK refitter for nuclear-powered submarines

The Ministry of Defence (MoD) is assessing the effectiveness of the base and those at Portsmouth and Faslane.

Its aim is to make sure as much money as possible is freed for frontline operations, the MoD said on Monday.

Plymouth naval base has close ties with neighbouring Devonport dockyard, the UK's sole refitting site for nuclear-powered submarines.

The base itself employs about 2,500 people and Devonport, owned by DML, employs about 5,000.

Jobs struggle

Devonport puts about �360m into the Devon and Cornwall economy every year - about 2% of the total - and about 400 local firms also have contracts with the yard.

Peter Gripaios, professor of applied economics at the University of Plymouth, said closing the base would put the city "in a very difficult economic situation".

He said: "It is of crucial importance to Plymouth, but there would be knock-on effects elsewhere.

Uncertainty about Trident refits could hit city investment

"There would be a very difficult adaptation to a lower level of economic activity.

"There are few examples of local economies transforming themselves after big local employers have moved out."

He said if there was further uncertainty about the refit facilities for Trident nuclear submarines, investors may be put off the city.

David Jamieson, former Labour MP for Devonport, said the argument for keeping the base was "very strong".

He said: "It is in a strategic position on the western approaches and we have the nuclear facility that no other naval base has."

But he said change was "inevitable" and the review may mean more work for the dockyard.

Closure 'inconceivable'

He said: "We have seen change over 20 or 30 years on an enormous scale in the dockyard and the naval base.

"The dockyard should be safe for a considerable number of years with its Trident work.

"I find it inconceivable [it] would close, but if there is any land released in this process we should be looking at how to create new jobs."

Recommendations from the review are expected to be presented to the government in the spring of next year.