The federal Opposition Liberals say they will table a private member's bill to reinstate the mandatory long-form census when Parliament returns next month.

Liberal finance critic John McCallum says there is still time to reinstate the mandatory long-form census before it is sent out next spring. (CBC)Liberal finance critic John McCallum told reporters on Thursday there is still time for the Conservative government to "come to its senses" and reverse its decision to scrap the spring 2011 mandatory long-form census and replace it with a voluntary survey.

The bill will call for 20 per cent of households to receive the mandatory long form — the same percentage as in previous census years. It would also remove the threat of jail time for those who refuse to fill out the form, McCallum said.

"We're very hopeful that we can get it through in time," he said, noting that more than 300 groups have publicly opposed the government's decision.

The Conservatives have been under fire on the census issue since Industry Minister Tony Clement announced the plan in late June to end the mandatory long-form survey.

Clement and Prime Minister Stephen Harper have said it is not appropriate for Canadians to be threatened with jail time or fines for refusing to provide answers to intrusive questions to representatives of the state.

Earlier this month, Clement announced two questions on languages would be added to the mandatory short-form census to fulfil the government's legal obligations under the Official Languages Act.