A Labour MP is calling for the government to consider national security after claims that six more Royal Navy warships may be mothballed.
HMS Southampton is one of the ships claimed to be under threat
Portsmouth MP Sarah McCarthy-Fry said she would lobby ministers to ensure military considerations were put first.
The Daily Telegraph has named the six vessels it says are being considered for "extended readiness", putting them up to 18 months from service.
The Ministry of Defence says no decision has been made on the fleet.
According to the Telegraph, the ships under threat of being withdrawn from active service are Type 22 frigates Cumberland, Chatham, Cornwall and Campbeltown and two Type 42 destroyers Southampton and Exeter.
These are in addition to the 13 ships which the Royal Navy has already placed in extended readiness.
The MoD says that of these, only HMS Invincible is around 18 months away from being ready for active service, but was unable to reveal how long it would take to make ready the other 12 vessels.
Ms McCarthy-Fry said: "It's a concern for Portsmouth, the home of the Royal Navy, especially as we already have the Naval base review.
"I will be pressing ministers to make decisions based on what we need our navy to do. They should not be making them purely on the basis of cost.
"The first consideration has to be our national security, then you look at the role of the navy in that."
An MoD spokesman said: "We currently have no plans to cut ship numbers.
"We routinely review whether resources are allocated where our frontline forces need them most. No decisions have been taken in this case."
He added that the MoD was building new destroyers, attack submarines, and support ships for the Royal Navy and planned to sign the production contract this year for two new aircraft carriers.
The spokesman also said reports that Portsmouth dockyard would close were "complete speculation".
He said: "We are reviewing our bases, and have undertaken to make savings, but no decisions have been taken."