OTTAWA - Parliamentarians are in the final stages of passing a prison-sentence bill without fully understanding the price tag or the repercussions on prison conditions -- despite some estimates that the new measures could cost hundreds of millions of dollars.

Bill C-25 would put an end to the common practice of giving criminals a two-for-one credit for time served in jail before being sentenced. Instead, the bill would have judges give them a straight one-for-one credit for time served.

But MPs and senators have not been able to figure out how much it will cost to implement, or gauge how the prison population will be affected.

Officials have costed the proposal, but say they can't release their numbers because of cabinet confidentiality. Data from Statistics Canada, however, point to at least a 10 per cent increase in the federal prison population, and costs well over $100 million a year.

It's a cost the Tories say is well worth it.

"We're certainly going to make our decisions on the criminal code based on how do we keep the community safe. We're not going to make it based on if it's going to save a couple of bucks here and there," Public Safety Minister Peter Van Loan said in an interview.

"The cost of obviously allowing murderers or rapists out on the street early, to re-offend, is something that is far too great to have that happen (than) trying to save a few bucks here and there."

The aim is to make criminals serve the time that they were actually sentenced, rather than give them extra credit for time in custody before their trials, where conditions are harsh.

The bill comes partly at the behest of some provinces who complain that their remand facilities and courts are clogged up by the existing system. The government has also argued that prisoners are gaming the system to get out of jail early. They claim that many unsentenced prisoners fight to stay in remand longer, so that they can avoid long stays in sentenced custody.

"The real story here is not one of cost, or capital or capacity," said Van Loan.

"The real story here is do you think criminals should actually be spending time in jail for the offences they commit, or do you think they should be let out early on whatever excuse you can come up with."

Faced with accusations of being soft on crime, opposition MPs did not block C-25 in the House of Commons. But senators say they want to have a better idea of the cost as well as the practical effects of the bill.

"We, as legislators, are requested to accept this bill without the proper figures and without understanding its impact," said Liberal Senator Serge Joyal at a recent committee hearing.

"You will understand that it is difficult for us to move on with this."

C-25 is now stalled in the Senate as Liberal senators, who dominate the upper house, question its effectiveness. They've proposed significant amendments, and could decide this week to send the bill back to the Commons.

The added costs stem from the fact the measures would likely extend the length of time many prisoners spend in the corrections system, and would also push hundreds of prisoners from provincial institutions into federal institutions.

Justice Minister Rob Nicholson, and now Van Loan, have said repeatedly that the corrections system has enough capacity to handle the influx. But Don Head, commissioner of Correctional Services Canada, told the Senate committee examining the bill that the number of prisoners will definitely rise, and will require an expansion of accommodation.

Until new institutions can be built, additional prisoners will have to double-bunk with existing prisoners, he said, or stay in trailers. Corrections will also have to invest in programming, training, education and intervention, he added.

"When I hear about increased double-bunking and temporary accommodation measures, certain alarms begin to go off, because the stated standard for federal corrections is one person, one cell," said Howard Sapers, correctional investigator of Canada, the ombudsman for federal offenders.

Already, federal prisons are overcrowded and unable to deal properly with the rising toll in mental illness, drug addiction, cultural diversity and gang affiliation, Sapers said.

"If the system is already burdened ... simply adding more numbers without more resources is going to overburden the system and cause it to fail."

Statistics Canada experts said the federal system could expect a 10 per cent increase in the number of prisoners, because of the change in law, all else being equal.

That means the federal prison population would grow by 1,300 each year, Sapers said. At an average cost of $80,000 for each prisoner, operating costs alone would grow by $104 million, he said.

But that number does not include the cost of keeping prisoners in custody longer, nor does it include the cost of developing new programs or building new institutions.

While Correctional Services Canada has been given hefty increases to its capital budget, the costs of implementing C-25 have not been factored in, Head testified. A new jail would cost between $20 million and $80 million.

"It's potentially hundreds of millions, plus" to implement the bill as it is, said MP Joe Comartin, the NDP's justice critic.

He estimates there are about 9,000 people now in remand, and 6,000 in federal prisons. If the legislation is passed as is, the pattern would reverse.

But he and other parliamentarians complained that they have not been shown evidence of how the change in sentencing practice would actually affect the prison population.

Experts at the House and Senate committees frequently testified that there is only limited anecdotal evidence suggesting prisoners are gaming the system. They said the number of people in remand is growing mainly because of new laws, changes in the way bail is granted and backlog in the courts.

So because no one has a firm idea about how the prison system would change, it's hard to determine exactly how much it would cost to implement, said Anthony Doob, professor of criminology at the University of Toronto.

"It's actually very difficult to figure out. It depends on things we really don't know."