HALIFAX -- Premier Stephen McNeil says he's awaiting clarification on how many Arctic patrol ships will be built in Halifax after the parliamentary budget officer concluded the federal government has not budgeted enough money to buy between six to eight of the vessels as promised.

McNeil said he wrote to Prime Minister Stephen Harper last week about the matter and he expects that the number of ships to be built by the Irving shipyard to remain unchanged.

"It's our belief and our understanding that the federal government has made a commitment to deliver on the entire package that was promised so we will wait to hear from the prime minister," McNeil said Tuesday.

A report by the parliamentary budget officer says the federal government's $3.1-billion budget is only enough to build four of the ships, and that could drop to three if the project gets delayed by more than a year.

The office of Public Works Minister Diane Finley said the report is wrong because it is based on erroneous information, rough cost estimates for international vessels with varying capabilities and it was unable to find reliable contemporary Canadian data.

Parliamentary Budget Officer Jean-Denis Frechette said that's because the government refused to give his office the information it needed to complete its report.

Last week, Irving Shipbuilding president Kevin McCoy said he was confident the company will build six Arctic patrol vessels, adding that Ottawa has not changed its mind about the shipbuilding deal.

McCoy's comments came after industry and military sources told The Canadian Press the government has scaled back its original plan to buy between six and eight vessels.

The sources said Ottawa would opt to buy five of the ships with an option for a sixth.