Joan Beatty made a mistake leaving the NDP to run for the Liberals federally and the decision will cost her at the ballot box, Saskatchewan NDP Leader Lorne Calvert says.

The Liberals said Friday that Beatty, the MLA for Cumberland, will run in the northern riding of Desnethé-Missinippi-Churchill River in the federal byelection.

The announcement came less than two months after Beatty was re-elected in the general provincial election.

"I'm disappointed," Calvert said Monday. "I think it's a mistake and I think there will be for Joan a political price to pay.… Her prospects of being elected, I think, are diminished both by leaving her political seat and by moving to the Liberal party."

Beatty said Friday she decided to join the Liberals to work for positive change in the north.

Calvert said he wished her well, but added she could have accomplished more in the NDP caucus than as a possible backbencher with the federal Liberals.

The byelection to replace Liberal MP Gary Merasty, who resigned last August, will be held March 17. Merasty went to work for a mining company.

The appointment of Beatty by Liberal Leader Stéphane Dion short-circuited what could have been a lively candidate race.

Former Progressive Conservative leadership candidate David Orchard is now a Liberal and had been hoping to run in Desnethé-Missinippi-Churchill River. Another northerner, John Dorion, was also expected to make a bid to represent the Liberals.

Dion's decision to appoint his own candidate has rankled some party supporters who say they would have liked to make the choice themselves.

Native leader Jim Durocher, who has considered himself a lifelong Liberal and ran for the party in the north twice, says he's considering leaving the party altogether.

Durocher, an Orchard supporter, said the Liberals have taken away the chance for the party faithful to express themselves.

"You should never, ever do anything to touch the democratic process that's in place, because a lot of people use that, and that's their only way of expressing themselves," he said.

However, the Liberals' national campaign co-chair, Senator David Smith, said there were perfectly good reasons for appointing Beatty, who was Saskatchewan's first First Nations cabinet minister when she was in Calvert's cabinet.

The party has set a goal of having one out of every three Liberal candidates be a woman. Passing up a seasoned politician like Beatty would be missing a great opportunity, Smith said.

"We want to have more women across the country and it doesn't always work out in the nomination process that we get the number that we want," he said. "Her credentials are very very strong and she's got a tremendous record."