TORONTO -- The Canadian Broadcasting Corp. on Monday locked out about 5,500 unionized employees and scaled back its radio and TV programming as the public broadcaster's biggest-ever work stoppage got under way.

The CBC's main network relied on reruns, and 24-hour cable news channel CBC Newsworld went to documentary fare and BBC World newscasts as an indefinite management lockout went into effect at 12:01 a.m. Monday.

CBC management, unveiling a "detailed contingency plan" for programming during the work stoppage, said it would air key revenue-generating Canadian Football League and upcoming National Hockey League games on its main network but without the play-by-play commentary normally provided by unionized staff.

And CBC radio promised hourly newscasts by management announcers, programming reruns and music fare for the length of the labor dispute.

Richard Stursberg, CBC's executive vp television, told reporters during a morning conference call that 11th-hour bargaining talks during the weekend fell apart over the number of workers that CBC management can hire under a temporary contract as opposed to establishing permanent positions.

"We operate in what is the most competitive media environment in the world. If we're going to succeed, the corporation needs the flexibility and quality of staff needed to provide the best programming to Canadians," he said.

Executives of the Canadian Media Guild, representing the public broadcaster's on-air, production, technical and administrative employees now walking the picket line nationwide, told the media outside the CBC's Toronto headquarters that the broadcaster's government-appointed board of directors should intervene and end the labor stoppage.

"They know this lockout feels wrong. It's an unnecessarily aggressive action by the senior management of this crown corporation," CMG president Lise Lareau said.

The CMG contends that about 30% of the CBC's work force is already nonpermanent, giving public broadcasters whatever flexibility they need in a changing broadcast landscape.

Stursberg argued that the 30% nonpermanent work force includes about 25% of CBC employees that work on a temporary basis, filling in for permanent workers on sick leave or special assignments, for example.

That leaves roughly 5% of the existing CBC work force in short-term contractual positions, a pool of workers that the public broadcaster wants to enlarge, where needed.

"The existing permanent positions will remain so. But as turnover occurs, we want the ability to determine whether jobs are permanent or short-term," Stursberg said.

The last CBC work stoppage occurred in 2001 when technical workers walked the picket line to secure a new collective agreement.

But the recent amalgamation of unionized journalists and technical workers at the CBC means the public broadcaster faces its largest-ever work stoppage.

The CMG's Lareau said CBC management demanded "untenable concessions" during recent talks on a new collective agreement.

"They wanted a work force that would, over time, become mostly temporary," she argued.

CBC employees have been without a contract since March 2004. Employees in Quebec and Moncton, New Brunswick -- or about 5% of the CBC's work force -- belong to a separate union and are expected to continue working through the management lockout.