WINNIPEG — NDP Leader Jack Layton is calling for a referendum on the abolition of the Senate, an institution he describes as "outdated and obsolete."

"It's a 19th-century institution that has no place in a modern democracy in the 21st century," Layton told party organizers Sunday in Winnipeg.

"It's undemocratic because (senators) are appointed by prime ministers who then are turfed out of office. But these senators end up leaving a long shadow of their continued presence in the legislative context."

Layton has long called for the upper chamber to be done away with. The idea for a nationwide vote on the issue was floated two weeks ago by Conservative Senator Hugh Segal, who favours maintaining the upper house. He said a referendum could lead to important reforms if a majority of Canadians voted to keep the upper chamber.

Layton, albeit with different motives, is trying to put Segal's idea on the floor of the Commons. He said the NDP will introduce a motion calling for a referendum in the coming weeks, and is hoping Prime Minister Stephen Harper will allow Tory members to vote freely on the issue.

The referendum would not be costly, Layton said, because it could be held in conjunction with the next federal election.

One obstacle to Layton's plan, however, is the fact that the referendum results could be very hard to translate into action.

Constitutional law prevents the federal government from making such major changes unilaterally. It would need the support of at least seven - and perhaps all 10 - provinces. Experts are divided over which amending formula would have to be followed in any move to abolish the Senate.

Four provinces - British Columbia, Ontario, Saskatchewan and Manitoba - are on record as favouring outright abolition of the Senate. But Quebec's Liberal government has already indicated it would oppose the plan. Support may also be hard to find in the Atlantic provinces, whose populations are over-represented in the upper chamber.

The prime minister has threatened to have the Senate "vanish" if it does not undergo reform. A bill that would have limited senatorial terms to eight years was blocked by the Liberal-dominated upper chamber this year.

Liberal senators said they were responding to concerns from provincial governments, which believe the proposed term limits require a constitutional amendment approved by at least seven provinces.

Still, Layton insists a referendum is well worth the effort.

"Why don't we start by finding out how Canadians feel about it? That seems to be to be a democratic approach."