OTTAWA - The NDP says it will propose legislation to limit the power of the prime minister to suspend Parliament.

Parliament should be prorogued only when a majority of MPs in the House of Commons vote to allow it, party leader Jack Layton said Wednesday.

Legislation to that effect would ensure "prorogation happens when it is needed, not simply when the prime minister feels like it," he said following an NDP caucus retreat.

All three opposition parties have vociferously condemned Prime Minister Stephen Harper's decision to suspend Parliament until March 3, joining a surprisingly robust groundswell of public outrage that appears to have fuelled a slide in Conservative party popularity.

Protest rallies are planned for Saturday on Parliament Hill and elsewhere across the country.

Opposition MPs intend to return to work Monday, as originally scheduled, in defiance of the prime minister. And they intend to revive hearings into the Afghan detainee controversy -- the issue critics believe Harper was trying to silence when he shut Parliament down.

Prorogation put an end to the special committee that had been investigating allegations the government turned a blind eye to evidence that detainees turned over by Canadian soldiers to Afghan authorities were later tortured.

Layton said opposition members of the committee have agreed to resume hearings on an unofficial basis, starting Feb. 3.

"Parliament must be able to do its work. The prime minister must be held to account," said Layton, billing himself as a disciple of "a new politics, a grassroots politics driven by Canadians."

Liberal Leader Michael Ignatieff also wrapped up a caucus retreat Wednesday, excoriating Harper as a prime minister who "doesn't understand Canadian democracy."

"He gambled on the cynicism, disenchantment and disillusion of Canadians . . . He gambled wrong."

While all opposition parties have railed against prorogation, Layton is the first leader to propose a legal remedy -albeit one that appears to have little chance of success.

An aide to Layton said the NDP will draft legislation in hopes that Harper will adopt it as a government bill -- a highly unlikely scenario. Barring that, the NDP will introduce a private member's bill. But that could take months, or even years, to be put to a vote and, even then, might not muster enough opposition support to pass.

Ignatieff last week defended prorogation as a legitimate prime ministerial power, although he said he would never use it simply to avoid "a tight spot" as Harper has repeatedly done.

Ignatieff said Liberal MPs will hold a series of roundtable discussions next week. One, on democratic governance, is to feature the heads of three government watchdog agencies who were fired or replaced after running afoul of the Harper government.

Like Layton, Ignatieff talked of a new way of doing politics, promising that his party's policy renewal process -- slated to culminate at a "thinkers" conference in March -- will be open, through the Internet, to all Canadians.

As part of that new "bottom-up" grassroots engagement, Ignatieff told caucus members he wants to excise the phrase "natural governing party" from the Liberal lexicon.

The decades-old moniker was originally meant to be descriptive, in recognition that Liberals have formed the government more than two-thirds of the time since the Second World War. In recent years, it's been seen more as a sign of Liberal arrogance -- a sense that they're entitled to win elections, no matter what they put on offer.

"If I can achieve one thing as leader of this party, it's to get that out of our vocabulary," Ignatieff said. "We have to earn the confidence and trust of Canadians every single day, voter by voter."