OTTAWA -- The federal government is trying to keep its multibillion-dollar plan to build new warships for the navy from capsizing by rejecting a French and Italian consortium's controversial proposal.

Paris-based Naval Group and Italian firm Fincantieri say they can build 15 new ships to replace the Royal Canadian Navy's frigates and destroyers for much less than the $60 billion budgeted for those vessels.

But the government says it will not consider the offer because the two companies did not follow the established process for submitting such proposals, the deadline for which fell last Thursday.

In a strongly worded statement, officials say accepting such a proposal would be unfair, establish a harmful precedent and ultimately threaten the government's ability to acquire ships for the navy.

The statement also attacks the companies' claims of being able to build ships at a discount, calling it "far from evident."

The Naval Group-Fincantieri proposal is the latest wrinkle in the largest planned military purchase in Canadian history, which is not expected to result in any ships being in the water until the mid-2020s.