David Cameron was asked questions about the naval base and dockyard
David Cameron has stopped short of guaranteeing the Conservatives would safeguard the future of Devonport dockyard if they win the election.
But speaking during a visit to Plymouth he did acknowledge the city is a "vital part" of the British defence industry and needs investment.
The local Labour MP Linda Gilroy said she would continue to "stand-up" for the dockyard and naval base.
The Liberal Democrats said they hoped Devonport "flourished" for years.
Mr Cameron was asked a number of questions about Devonport during a question and answer session at Sir John Hunt Community Sports College.
He said: "Plymouth is a vital part of our defences and a vital part of the Royal Navy and needs to have investment... but we do need to have a proper defence review."
He said if the Conservatives win the election a defence review would be "up and running within weeks" and tasked to report back in the autumn.
Of the government's plans to move a number of the navy's frigates from Devonport to Portsmouth and its nuclear submarines to Faslane in Scotland, he said it was "important not to put all our eggs in one basket".
The naval base and dockyard support about 24,000 jobs
Linda Gilroy said: "I will continue standing-up for the dockyard and naval base if re-elected, but, equally importantly, for the armed forces, 29 Commando and 3 Commando Brigade.
"They're just as important to Plymouth as the naval base and dockyard."
The Liberal Democrat's defence spokesman and MP for North Devon, Nick Harvey, said: "We take Devonport dockyard very seriously and we hope to see it flourish and prosper for many years to come.
"It is a vital part of Britain's defence infrastructure."
The naval base and the commercial dockyard is currently estimated to support about 24,000 jobs, according to a 2009 University of Plymouth study.