Accused by opposition parties of misleading Canadians over the ballooning costs of the F-35 jet procurement contract, the Parliamentary Secretary for the Minister of National Defence says the government is looking at alternative options to replace Canada’s aging fleet of fighter jets.

Ahead of the release of a report on the cost of buying and servicing new fighter jets, the junior defence minister Conservative MP Chris Alexander confirmed other options besides the F-35 will be considered under the government’s seven-point plan for aircraft replacement, and insisted a decision on the controversial procurement has not yet been set in stone.

“The numbers we get this week will start to put to rest the whole question of verified cost for one of the options,” Alexander told CTV’s Question Period on Sunday.

"We are looking at other options," he said, explaining that there will be a full options analysis under the seven-point plan.

“There were various statements in the past that amounted to commitment intentions," Alexander said.

"The situation has changed, cost outlook has changed, the Auditor-General came out with a report that we had to take very seriously earlier this year and we accepted his recommendation and we put in place a seven-point plan to get us to the point where a decision could made, not just with regard to one option, but with regard to all the options on the basis of verified cost."

The government announced in 2010 that it was purchasing the F-35s from jet manufacturer Lockheed Martin to replace the Canadian Forces' aging fleet of CF-18 fighter jets.

A report to be released publicly on Tuesday is expected to reveal that the cost of 65 jets over 36 years will far exceed the initial estimates pegged between $14 and 16 billion. Earlier reports from both Auditor General Michael Ferguson and Parliamentary Budget Officer Kevin Page said the government's estimates were far too low.

But Alexander defended his government, saying there "absolutely not" a deliberate attempt by the Conservative’s to under-sell the cost of the jets.

"The government can’t take a decision about replacing the CF-18s, about buying a new aircraft until it has very, very credible verified cost assumptions for all the possible options. We haven’t had those until now," he said, adding the government will have a "much better understanding" of those costs when the report is released Tuesday.

Alexander said initial numbers didn’t factor in the yearly operational costs of the jets, pegged at about $1 billion "give or take" for most of the options being considered.

Liberal Defence critic John McKay accused the Conservatives of revising history, and misleading Canadians on procurement costing over the last three years.

"It is a catastrophic failure of oversight that should give every Canadian pause," McKay said.

In light of leaks late last week, Liberal Leader Bob Rae called on Defence Minister Peter MacKay to resign.

On Sunday, NDP Defence Critic Jack Harris said "virtually everything" the government has said about the procurement has been untrue, and that the only way to "cushion the blow" on being caught publicly for lowballing cost estimates was to release more documents.

"If we can’t make decision without having the numbers, why was there an announcement on July 16, 2010 that we were buying 65 airplanes and these are the ones we were buying," he told Question Period.

"The problem was … they were using numbers that were provided by Lockheed Martin in about 2002."

The government is now changing its jet procurement process to include decision-making by senior officials and advice from independent experts.

CTV News has learned that those experts will include retired Lt.-General Charles Bouchard, who led the NATO mission in Libya, former auditor general Denis Desautels and University of Ottawa professor Philippe Lagasse, a critic of the F-35 plan.

The government is currently reviewing the F-35 report and plans to respond with a "comprehensive public update" next week, before the House of Commons rises for Christmas break on Dec. 14.