British Conservative Leader David Cameron, centre, speaks during a televised debate with Nick Clegg of the Liberal Democrats, left, and Labour Leader Gordon Brown. (Rob Evans/Associated Press)

The old order in British politics seems thoroughly shattered following the country's first-ever televised leaders' debates, with two new weekend polls suggesting the country's traditional third party, the Liberal Democrats, has an unprecedented chance at being in government.

The polls were taken after Thursday's TV debate, the first ever in a British election campaign and the first of three to be held before the May 6 vote. Both put Prime Minister Gordon Brown's Labour Party in third place in a horse race with Liberal Democratic Leader Nick Clegg and the Conservative Party's David Cameron.

The Lib Dems, as they're widely known in Britain, haven't topped a national poll since 1983, and haven't been in government since their predecessor, the Liberal Party, ruled in the early 20th century.

Liberal Democratic Leader Nick Clegg speaks to students in northern England on Friday. Polls suggest he's shaken up Britain's traditional political order. (Chris Radburn/Reuters)

A poll for The Sun newspaper taken Friday had the Tories at 33 per cent, the Lib Dems at 30 and Labour at 28. A Daily Mail poll had Clegg's party in front at 32 per cent, with the Conservatives at 31 and Labour at 28.

The results suggest Britain may be headed for its first minority Parliament since February 1974, which lasted all of eight months before another election was called.

Both surveys also hint at a looming constitutional crisis. Because of the British first-past-the-post voting system, seat projections show Labour could keep a plurality in the House of Commons, while the Lib Dems may win the popular vote but still finish a distant third in the constituency count.

The Liberal Democrats — a left-leaning party that opposed the 2003 Iraq invasion, favours greenhouse-gas reductions and would hike taxes on mansions — have for years appealed for Britain to introduce a more proportional form of representation.

"The game changer really would be if a coalition allowed the Liberal Democrats to get the electoral reforms they want," said Steven Fielding, a professor politics at the University of Nottingham.

Debates a big boost to Clegg

Clegg's popularity surged in the wake of Thursday's debate, according to the Sun's survey, with nearly twice as many voters saying he would make the best prime minister after than before the debate.

The Liberal Democrats had been polling around 20 per cent before the TV encounter, but viewers rated 43-year-old Clegg the most honest, charismatic and relaxed leader, and near-majorities of respondents in several surveys said he'd won the contest.

Clegg hit important marks with the audience: He labelled the two largest parties "old and tired," called for an overhaul of the electoral system and promised to clean up politics, a reference to a scandal last year in which MPs claimed expenses for everything from pornography to moat maintenance.

His polling bump could be the merely ephemeral enthusiasm of a charmed public, but if not, it would upend Britain's traditional two-party order, in place since the 1920s. The Lib Dems' rocketing fortunes also threaten to derail the hopes of Tory Leader Cameron, who had been expected to capture 10 Downing Street from a flagging Brown.

If the Conservatives still capture the most seats but not a majority, it's unclear whether they could successfully court Clegg into a coalition. His party has never allied with the Tories before except during wartime, while it did shore up Labour briefly in 1977.

One thing is certain: The Liberal Democrats are no longer the after-thought third party from elections of yore, and that means Labour and the Conservatives will have them squarely in their sights.

"Now that we've made this a three-horse race rather than a two-horse race, they're going to be coming for us," former party leader Paddy Ashdown told the BBC. "We've got to be ready for it."

With files from The Associated Press