The Liberal Democrats, the perennial third party in British politics, topped a pre-election opinion poll on Monday after a strong television performance from their leader brought a surprise surge in support.

The centrist Lib Dems and their multilingual leader Nick Clegg face increased scrutiny this week as ruling Labour and the opposition Conservatives seek to bring them down to earth in the run-up to the May 6 election.

A YouGov poll in the Sun newspaper gave the Lib Dems 33 percent of the vote, one point ahead of the Conservatives, with Labour, in power for 13 years, trailing with 26 percent.   

Under the quirks of Britain's first-past-the-post election system that would make the Conservatives the biggest party in the 650-seat parliament and give the Liberal Democrats about 130 seats -- almost double the number they have now.

That scenario would stop any party from winning an outright majority, allowing the Liberal Democrats to form a coalition with either the centre-right Conservatives or the centre-left Labour.   

Markets fear an inconclusive election leading to a so-called "hung parliament" as they believe it would jeopardise efforts to curb a budget deficit running in excess of 11 percent of GDP.

Britain's sterling currency fell sharply on Monday on concern about a hung parliament.
 Clegg, 43, transformed from virtual unknown to rising star after his showing in the first TV debate, set his sights high.   

"I want to be the next prime minister," he told a news conference. "There's a fluidity to this election which we haven't seen for perhaps a generation. I can't predict what is going to happen...all I know is that the old anchors, the old patterns, the old established routines are breaking down."    

The Conservatives have warned a vote for the Lib Dems could allow Labour Prime Minister Gordon Brown to cling on to power in a minority government.

The Lib Dems would appear more natural bedfellows with Labour in any kind of coalition. But if Labour win a lower percent of the popular vote than the Conservatives such an alliance would be hard for the Lib Dems to justify -- given their longstanding call for proportional representation.   

The Lib Dems appear to have struck a chord with voters disillusioned with politicians after a scandal over lawmakers' expenses which has hit the two biggest parties hardest.   

The party has also talked tough on banks and bonuses -- another target of public ire after the credit crisis.  Clegg, Brown and Conservative leader David Cameron will face off in another live televised debate on Thursday. - Reuters