OTTAWA - Justice Minister Rob Nicholson, saying it's time to promote "truth in sentencing," is bringing in legislation to curb the two-for-one credit commonly given to convicted criminals for time spent in pre-trial custody.

"I believe there is widespread support in this country to address this issue," Nicholson told reporters outside a Conservative caucus meeting on Wednesday.

He plans to introduce his bill Friday, and he's challenging opposition parties to fast-track it through the House of Commons.

If they're sincere about fighting crime, said the minister, "there should be no problem getting this passed in a day."

That hope quickly evaporated as the Liberals, NDP and Bloc Quebecois - despite their general support for the aims of the bill - dismissed any idea of rubber-stamping it in a single day.

The main justification for giving double credit for pre-trial detention has always been that it compensates inmates for so-called "dead time" spent in overcrowded provincial jails that lack proper rehabilitation programs.

It also makes up for the fact that pre-trial time doesn't count toward eventual parole or other early-release provisions that only kick in after formal sentencing.

Police, victims' rights groups and some provincial justice ministers have complained the system is being abused by prisoners who try to stretch their period in pre-trial custody to reduce their overall time behind bars.

Defence lawyers and criminologists dispute that claim, saying the primary reason for lengthy pre-trial delays in many jurisdictions is a shortage of judges, Crown attorneys and courtroom space.

The Criminal Code has never spelled out a two-for-one ratio for pre-trial time, but many judges have come to accept it as a standard rule of thumb. In exceptional cases, some have even given three-for-one credit.

In other high-profile prosecutions, however, judges have rejected the concept and treated pre-trial detention on the basis of straight time.

That was the case, for example, in the recent sentencing of Momin Khawaja, the first person charged under the federal Anti-Terrorism Act. He spent nearly five years in custody before being convicted, then got another 10 1/2 years on top of that.

Nicholson denied his planned legislation is a slap at judges who adhere to the double-time rule of thumb.

"I trust the judicial system of this country, it works well," he said., But he went on to insist that it's still up to Parliament to give "guidance" to the judiciary by laying down clear rules.

The precise terms of the government bill won't be made public until it's tabled Friday, a fact noted with some concern by opposition spokesmen.

Liberal justice critic Dominic LeBlanc called it "a little bizarre" for Nicholson to demand same-day passage before MPs had seen the fine print of the bill.

LeBlanc said, however, he's willing to discuss "expediting" the legislation once he's examine it to make sure there are no surprise provisions.

The Liberals started pressing the Tories to act on the issue weeks ago, after the British Columbia government sought changes to the two-for-one rule to help combat gang violence in Vancouver.

Joe Comartin, the NDP justice critic, said he believes that, to survive a potential court challenge under the Charter of Rights, any bill will have to leave room for judges to continue granting extra credit for pre-trial custody in exceptional circumstances.

The NDP agrees credit can be reduced in most cases, he said, but "there's no way" it will agree to one-day passage of the bill.

Real Menard, the Bloc Quebecois justice critic, agreed the concept of double-time is "anachronistic" and ought to be replaced by credit on a straight-time basis.

But he said the bill should go to committee at least briefly so interested groups can state their views.

"Speed is the enemy of intelligence," said Menard. "You have to take the time to hear people."