Uncertainty remains over the future of Portsmouth's naval base despite encouraging signals from Prime Minister Tony Blair.
More than 17,000 people are employed at Portsmouth's base
In a keynote lecture at the Devonport naval base in Plymouth on Friday, Mr Blair said a "massive" ship-building programme was still to come.
But a Ministry of Defence (MoD) review could make cuts at Portsmouth.
Portsmouth south Liberal Democrat MP Mike Hancock told BBC News Mr Blair makes Navy cuts at his "peril".
The government had made a "big effort" to equip the Navy for what was asked of it, said Mr Blair.
"For our part, in government, it will mean increased expenditure on equipment, personnel and the conditions of our armed forces - not in the short run, but for the long term," he said.
"All of this is progress, but we know it's progress against a challenge that grows ever bigger."
Portsmouth's naval dockyard currently employs more than 17,000 people and is home to about two-thirds of the Royal Navy's surface ships.
Liberal Democrat Mr Hancock said it would be "a very unwise prime minister and government who went against the wishes of the British people" who want a strong Navy.
"If the government is going to insist on on-going worldwide commitments for our fleet then they have to ensure three things," he said.
"One, we have the ships, two, we have the men and women, and three, we have the three home ports to actually properly base and support the ships of the Royal Navy something that traditionally the people of this country have taken for granted.
He added: "You cut your Navy at your peril.
"If we are going to be a deep water Navy, a power which we want to see exercised around the world then the government are going to have to accept that that comes at a price."