Prime Minister Stephen Harper's latest reasoning behind his decision to prorogue Parliament has left many scratching their heads, and a former top Tory advisor says the government hasn't been "credible" in their explanation of the decision.

"I fault the government for not coming forward with a more adult explanation of why this is necessary," Harper's former chief of staff, Tom Flanagan, told CTV News Channel's Power Play on Tuesday.

"I think the government's talking points haven't been entirely credible."

On Monday, Harper told the Business News Network that financial markets are concerned about the stability of a minority government, claiming proroguing avoids instability.

Harper had previously said the government needed to change its agenda as the economy moves into recovery as a reason for proroguing.

Flanagan, a political scientist at the University of Calgary, says he supports the prorogation but thinks Harper's latest justification for it doesn't add up.

"I think markets are concerned about economic fundamentals. In 2009 ... we had the greatest single advance in the TSX in history and it was in a year of ... constant expectations for an election," Flanagan said. "I think investors look at market fundamentals, they don't look at the antics of politicians."

Liberal Leader Michael Ignatieff laughed off Harper's statement, claiming it was one of the best jokes he had heard in a while.

"The idea that democracy creates instability is ridiculous," he told reporters in Montreal on Tuesday.

"What does he want? To cancel Parliament altogether so we can have the stability of a prime minister without any limits on his power?"

Many pundits have said the Conservatives may be somewhat surprised by the reaction to move forward with the second prorogation in a year.

More than 170,000 people have joined a Facebook group called Canadians Against Proroguing Parliament and another 175 political scientists signed a letter condemning the move.

Even the respected right-winged Economist magazine ran an editorial slamming the move.

Flanagan dismissed the Canadian political scientists' letter, saying there was nothing wrong with proroguing.

"This is part of the discretion of the prime minister . . . there's nothing unconstitutional about it," he said.

Flanagan added that the government's explanation of proroguing was "skirting the real issue -- which is the harm the opposition parties are trying to do to the Canadian Forces" regarding the Afghan detainee issue.

Flanagan served as Harper's chief of staff from 2001 to 2005.