The Liberals are demanding the federal government reverse its decision to scrap the mandatory long census form, saying they will introduce legislation to protect a mandatory long-form census if necessary.

The Conservative government announced last week that it is eliminating the mandatory long census form for the 2011 census, replacing it with a voluntary national household survey.

"There is no doubt the Tories hoped this decision would be ignored," said Liberal MP Marlene Jennings at a news conference Wednesday. "It was taken in secret, with no consultation, and it was leaked on the eve of national holidays last week. They can't get away with it that easy. We won't let them get away with it that easy."

All Canadians will still receive a mandatory short census. One in three households will be sent the new household survey as well. Previously, one in five households were sent the mandatory long-form census.

Senior statisticians at Statistics Canada have conceded the change will make it more difficult to obtain reliable, detailed information.

"The decision is dangerous and must be reversed," said Jennings. By making the survey voluntary, its findings will likely be skewed and rendered irrelevant. Municipalities, provincial governments, community groups, business and other organizations that depend on the data for developing sound policy, will be negatively impacted."

Jennings said that Industry Minister Tony Clement has not adequately explained the reasons for the decision and that if the concerns he has raised over intrusiveness and privacy are legitimate, he should hold public consultations on the issue first.

She said that if Clement does not reverse the decision, the Liberals would introduce a private member's bill in the fall to amend the Statistics Act in a way that, if passed, would ensure the undertaking of a mandatory long-form census.

She argued that Clement has shown in postings to the social media site Twitter that he does not understand how the mandatory nature of the long-form census allows Statistics Canada to properly weight the short form data. Clement debated sample size and data weighting with other posters, including an economist.

"(That's) something Mr. Clement seemed not to understand when he was tweeting yesterday, so maybe he should take a stats course," she said.

In an email, Clement spokesperson Erik Waddell said that, "beyond the provision of basic information, the government does not believe it is appropriate to demand detailed information from its citizens."

"We believe the new National Household Survey will enable us to obtain the quality data Canadians need, without mandating the provision of personal information by citizens."

Waddell also said, "The government will not be revisiting this issue."