OTTAWA — The federal Liberals are asking Parliament's budget watchdog to look into the government's planned purchase of billions of dollars worth of F-35 fighter jets.

Liberal defence critic Ujjal Dosanjh has written to the parliamentary budget officer, Kevin Page, asking about the propriety of the deal to buy 65 of the high-tech jets at a total cost of $16 billion.

Dosanjh says the decision to forgo a competitive process in favour of the F-35 has to be examined.

He says it's the latest in a series of defence purchases that went without competitive bidding.

In recent years, the government has purchased helicopters and two different transport planes on a sole-source basis, without seeking competitive bids from other manufacturers.

Dosanjh says that may saddle the taxpayer with more than $5 billion in extra costs.

"It appears the Harper government may be deliberately choosing not to save money at a time when it is running the largest deficit in Canadian history," he said in his letter to Page.

He asked Page to look at practices in other countries.

"I would like a comparative analysis of the costs and benefits that different countries have experienced when acquiring the same piece of military equipment, where one country engaged in a competitive bidding process and the other country opted to make the purchase through a sole-sourced contract."

Defence Minister Peter MacKay announced last week that the government would buy the stealthy joint strike fighter from Lockheed Martin.

"We need to ensure our fighter-aircraft fleet remains the best in the world to meet the threats of the 21st century," he said.

The jets themselves will cost about $9 billion, with a 20-year maintenance package pushing the total cost to $16 billion.

The first plane is to be delivered by 2016.

Canada has spent $160 million over the last decade on development of the aircraft.