OTTAWA - A price tag for part of the Conservatives' law-and-order agenda is about to be made public -- and the number is in the billions, far higher than any previous estimates.

The Parliamentary Budget Officer forecasts the cost of implementing just one of the Tories' many tough-on-crime bills is between $7 billion and $10 billion over the next five years.

Kevin Page's complex investigation into the budget implications of the so-called "Truth in Sentencing" legislation -- also known as the two-for-one sentencing law -- is expected to be made public early next week.

Sources familiar with the document told The Canadian Press the study concludes the provinces will have to pick up about three-quarters of the costs, while Ottawa pays the rest.

The cash-strapped governments of Quebec and Ontario will be particularly hard hit.

"The provinces have walked into this with their eyes closed," said Craig Jones, executive director of the John Howard Society of Canada.

The report is likely to provoke a showdown between the Page's office the government over the credibility of the analysis. Ottawa has always maintained that much of the increased costs could be absorbed by shuffling prisoners to jails where there's extra space, or by more double-bunking -- putting two prisoners in one cell.

Critics call that practice "chicken-caging" and say it would be a betrayal of Canada's international commitments to maintain corrections standards.

In an interview Tuesday, Public Safety Minister Vic Toews said $90 million has been set aside over this year and next to implement the law at the federal level, and expand existing facilities if need be.

"We're not exactly sure how much it will cost us. There are some low estimates, and some that would see more spent -- not more than $90 million."

The provinces should not see any increase in costs, Toews added, noting the impetus for the legislation came mainly from provincial attorneys-general.

Bill C-25 came into effect in February, and targets the length of criminal sentences. It aims to end the common practice of giving criminals a two-for-one credit for time spent in remand -- incarceration while suspects are waiting to be dealt with by the courts.

Under the new law, judges are required to count the time spent in pre-trial as straight time, in most cases.

As a result, many criminals will likely be in jail or prison far longer than before, putting a strain on crumbling infrastructure and tight budgets.

"The risk is that longer periods of time in federal custody will put additional pressures on an aging physical infrastructure and potentially increase risks to the safety and security of staff and offenders," warns a recent report from Correctional Service Canada.

But the practical effects of the legislation have never been thoroughly examined in public. The government, for example, has refused to release its internal analysis of impacts on prison populations and costs.

"It's always difficult to estimate what the impact is going to be," Toews said.

"Quite frankly, I'm not so sure that there will be a significant increase in our population because essentially we're dealing with the same people over and over again," he said.

They've been gaming the system to take advantage of two-for-one credits, using bail terms to pop in and out of remand to cut down on their time in custody, he said.

"Now, they'll stay put without intermittent releases on bail."

But the $90 million set aside by Ottawa will not be nearly enough, says the analysis done by the PBO.

Page devoted a third of his staff and six months to building statistical models, and double-checked the results with outside experts, to arrive at his conclusions.

Page has butted heads with the government previously, notably over deficit and spending projections issued by the Finance Department.

He was asked for the C-25 cost estimate by Liberal MP Mark Holland after The Canadian Press revealed last fall that costs could be large -- and that MPs passed the legislation without the benefit of a government estimate.

"It's going to show that the costs involved are mind-boggling," Holland said in an interview.

The PBO examined just one piece of the Tories' tough-on-crime strategy, and staff were frequently stymied by government refusals to hand over information.

Staff have now developed a model based on what has happened as a result of similar legislation in the United States, making it easier to determine the costs of other crime bills, Holland said.

"They're not tough on crime," he added. "If you look at where they're spending their money, they're building prisons.

"They're literally trying to create the same crime factories that were created in the United States, when the United States is running in the opposite direction."

Still, the Liberals backed C-25 when it was before the House of Commons. The bill moved largely unencumbered through the Commons and Senate last year, despite damning testimony from a range of experts.

Conservative and Liberal MPs voted in favour of the bill without knowing how the prison population would be affected. They also had no idea what the cost would be. Nor did they thoroughly examine the effects of the federal bill on provincial institutions.

When Liberal Senators asked questions about the costs, they were told that the government analysis was confidential because it was before cabinet.

Since the PBO did not have full disclosure from the government, it used Treasury Board estimates for the cost of building new prison cells and the cost of keeping inmates in jail longer. Staffers then plugged the Treasury Board numbers into a model based on flows of prisoners in parts of the United States.

Aware that the government would once again attack its credibility, the PBO also created a panel of outside experts to examine its numbers. The cost estimates will be presented as a range, to take into account the imprecision of their underlying assumptions.

"I no longer use the term 'crime agenda.' This is not a 'crime agenda'," said Jones of the John Howard Society, who was on the panel.

"It is a punishment agenda."