Opposition MPs demanded answers from the government on the F-35 fighter jet purchase Tuesday following a CBC News story that raised questions about the process used to choose the aircraft and whether it meets the requirements stipulated by the military.

Evan Solomon, host of Power & Politics, reported Monday that CBC News had seen a copy of the department of national defence's statement of operational requirements, a document that has not been released publicly. It indicated that the mandatory requirements for the jet that would be chosen to replace the aging CF-18s was written in June 2010.

That is only one month before Defence Minister Peter MacKay announced that the government would buy 65 of Lockheed Martin's F-35 planes, through the Joint Strike Fighter program. It also revealed that at least one of the mandatory requirements given by national defence is not met by the F-35 model.

One of the 28 mandatory requirements listed is for the plane's sensor requirements. The document says the plane must be capable of providing the pilot with a helmet that allows 360-degree, out-of-cockpit visual situational awareness in a no-light environment.

"According to the U.S. Department of Defence there are so many problems with this feature that they're actually designing a backup. In other words, the plane can't do it," Solomon reported.

Associate Minister of Defence Julian Fantino fielded questions during question period about the CBC News story on the F-35s.

NDP MP Matthew Kellway said the government tabled a response to an order paper question on Monday, the same day the story aired, that said the F-35 currently meets all of the military's stated requirements.

"Which document is the truth? The one for public consumption or the one kept secret?" Kellway asked.

"We will remain committed to the Joint Strike Fighter program," Fantino responded. "A budget has been identified, a contract has not been signed for a replacement aircraft and we will make sure that the air force and the men and women there have the necessary tools to do their job and that's the bottom line."

Prime Minister Stephen Harper was also asked about the procurement during a press conference in South Korea where he is wrapping up a trip to Asia.

He said Canada has participated in the F-35 development program with its allies for 15 years and the aerospace industry has received "hundreds of millions of dollars in contracts" because of it.

"We haven't yet signed a contract, as you know, we retain that flexibility but we are committed to continuing our aerospace sector's participation in the development of the F-35," Harper said.

Interim Liberal Leader Bob Rae said if the government is considering a model other than the F-35, it should be telling Canadians.

"There's obviously been a shift in position in the last several weeks," Rae said, referring to Fantino's change in messaging over the last few weeks. Fantino previously defended the F-35 vigorously but now says that a final contract to buy the planes hasn't been signed.

NDP Leader Thomas Mulcair said the documents seen by CBC News show that the government created a "bogus bidding process" because it appears as though it had already chosen the F-35 when the mandatory requirements were written.

"They tried to rig the process by defining something that only one plane could meet," Mulcair told reporters. "It's a very old strategy in government procurement, but even there we're now finding out the F-35 doesn't meet the bogus requirements that they were setting out in their rigged bid.

"They're bringing us down a corridor that can only result in one thing, the purchase of that one [plane] because their next argument is going to be 15 years later we can't start changing our mind," he said.

Alan Williams, a former defence department official who was involved in Canada signing on to the Joint Strike Fighter program, also says the proper procurement process wasn't followed.

But Christopher Alexander, parliamentary secretary to Defence Minister Peter MacKay, denied the allegations that the bidding process was rigged.

"Absolutely not and it's misleading Canadians to say so," he said on Tuesday's Power & Politics program.

When asked if he finds it unusual that the statement of requirements was written less than two months before the plan to buy the planes was announced, Alexander said "it is an exceptional project because it is a new technology that is still being developed."

Alexander said the plane is still under development and the government expects that it will fully meet all of the requirements.

U.S. Defence Secretary Leon Panetta, in Ottawa for a meeting Tuesday, said the program is subject to a high degree of oversight as the planes are developed. Canada, the United States and a number of other countries are jointly paying to develop the planes and buy them.

"We remain very confident that this plane can do everything it's being asked to do in terms of performance. We've been testing it and we continue to evaluate it as we proceed," he said.

Lockheed Martin, a U.S.-based company, said in a statement that it "has high confidence the F-35 program will meet Canada's requirements."