Conservative MPs fanned out across the country Monday to announce more than $150 million in expansions to eight prisons, with government tough-on-crime measures expected to keep more Canadians in jail for longer sentences.

The building boom, which is part of the government's five-year, $2 billion plan to enhance Canadian jails, will put 634 new beds at institutions in Quebec, Ontario, Saskatchewan and Alberta at a total cost of $158 million.

In Ontario, government whip Gordon O'Connor announced a $20 million expansion of the Pittsburgh and Frontenac institutions, while Industry Minister Tony Clement announced a $10 million expansion of Beaver Creek Institution. Each will receive a new 50-bed living unit, to be completed in 2012-2013.

In Quebec, MP Shelly Glover announced $73 million in funding for two new 96-bed living units Cowansville Institution, to be completed in 2012-2013, and a new 96-bed living unit at Donnacona Institution, to be completed in 2013-2014.

Laurie Hawn, parliamentary secretary to Defence Minister Peter MacKay, said the government will spend $55 million to add 96 beds to Edmonton Institution, as well as 90 beds at two facilities in Saskatchewan.

Hawn said Monday the announcements are part of the government's tough-on-crime stance, including its Truth in Sentencing Act, which eliminates two-for-one, pre-sentence jail credit for time served in custody before prisoners are convicted and sentenced.

"We believe in spending money in a focused way to keep Canadians safe and keep our communities safe, and that's what this is all about," Hawn told CTV's Power Play.

The announcements follow similar pledges made three months ago by Public Safety Minister Vic Toews, who announced a $155 million expansion of three other prisons in Ontario and two in Quebec.

The upgrades come as the Correctional Service of Canada copes with a federal inmate population of about 13,000, a number expected to grow as the federal government's anti-crime policies come into effect.

In his annual report issued late last year, Correctional Investigator Howard Sapers said that to cope with a swelling population, the CSC has increased so-called double-bunking -- putting two prisoners in a cell made for only one -- by about 50 per cent over the past five years.

Overcrowding increases the risk of tension and violence in jails, Sapers warned.

The CSC has said it plans to add 2,700 new beds to men's and women's facilities across the country in the coming years.

Former Canadian media baron Conrad Black, who served time in a U.S. prison on fraud and obstruction of justice charges, said there is no question that violent criminals must be segregated for the public's safety.

But he said there are grave societal implications of crowding people into prisons for long periods of time.

"The societal implications if you just keep people in prison for longer and under more severe conditions is that you will eventually release more embittered people less qualified to re-enter normal, law-abiding life than you would otherwise have had," Black told Power Play in a telephone interview from Florida. "And you will also inflict on the country and its taxpayers a completely unnecessary expense, all presumably in the pursuit of votes that, as far as I can see, this government has in the bag anyways."

Black said prisoners who will benefit from therapy should be treated so that when they are released, they are better able to cope with the problems that may have put them in jail in the first place, such as addiction or mental health issues.

Liberal MP Mark Holland said experiments in building so-called "super prisons" have failed in jurisdictions such as California, which spent billions of dollars building prisons after it enacted a three-strikes rule for offenders, but ended up with a reoffending rate of 70 per cent.

Holland said it is crime prevention strategies and programs aimed at treating mental health and addiction issues that will make communities safer.

"(The government is) creating these crime factories, where essentially people are going in for minor crimes and coming out major criminals, because the only solution that this government has for any sort of crime that happens is to incarcerate people, and that's been a disaster anywhere it's been tried," Holland told Power Play.

Hawn denied the government has cut crime-prevention programs, pointing out that in the past two years, the government has increased funding for such programs and recruiting at police forces is up across the country.

But he also said officials are looking at improving prison programs to better help prisoners re-enter society.

"We're looking at expanding areas of business, textiles, manufacturing, those sorts of things," Hawn said. "So when people do get out of prison having served the appropriate time for their crime, they do have some skills that they can bring to bear and they can become part of society again."