Liberal Democrats unveil election battle bus

(Getty Images)

The Liberal Democrats fired up its election battle bus on Monday, a day before Labour Prime Minister Gordon Brown is expected to name 6 May as polling day.

The centre-left party could hold the balance of power between Labour and the Conservatives if the election results in a hung parliament as opinion polls have suggested.

Liberal Democrat leader Nick Clegg arrived in a gold-coloured bus in the new London seat of Hampstead and Kilburn, one of several marginal seats that Labour will probably need to win to stay in power.

The Liberal Democrats, campaigning under the slogan 'Change that works for you', claim they only need to win over a few hundred voters to beat Labour in the north London constituency.

"I just want to get on with the campaign," Clegg told Sky News. "Let's get this campaign off to a really good flying start."

The economy is at the heart of all of the main three political parties' election campaigns, with each trying to score points over how best to bring down record government borrowing with the least damage to the recovery and public services.

"Labour will put your taxes up, the Conservatives will keep your taxes the same," Clegg said. "Only the Liberal Democrats have a plan to cut your taxes. If you want lower taxes you have only got one party to support."

Opinion polls suggest the party could win about 20 per cent of the popular vote, indicating it could struggle to beat its current allocation of seats in parliament of 63.