Mr Brown said oil prices are an international problem

Gordon Brown said rising prices were an international issue as he joined Labour candidate Jim Devine on his campaign.

SNP leader Alex Salmond said Mr Brown needed a "wake-up call" over oil prices and Scotland's economic performance.

Tory Gordon Lindhurst was joined by party leader Michael Howard, while Lib Dem Charles Dundas focused on crime.

After touring the Bausch and Lomb contact lens factory in Livingston, Mr Brown said the public were aware that oil prices were a world problem.

"We are pleased petrol prices fell over the weekend," he told the media.

Livingston by-election Peter Adams, UKIP John Allman, Alliance for Change Melville Brown, Independent Angela Constance, SNP Jim Devine, Labour Charles Dundas, Lib Dems Brian Gardner, SPGB Gordon Lindhurst, Tories Steven Nimmo, SSP David Robertson, Greens

"We will continue to put our case, particularly on Friday at the IMF and World Bank meetings in Washington, for all the major countries of the world to agree on a common strategy."

He rejected the SNP argument that an independent Scotland's economy would be supported by North Sea revenue.

"You can't build the whole future of your economy, or your arguments about a policy, around one raw material," he said.

On the nationalists' call for an oil fund for investment in Scotland's future, he said: "I think the SNP seem to forget in this argument that we have doubled public investment - that we have invested in the future.

"We have done more than anybody ever imagined in 1997 to invest in new hospitals and schools."

'VAT revenues'

Responding to media speculation, Mr Brown also insisted that no decision about changing the retirement age would be taken without a "national debate".

Lending his support to candidate Angela Constance, Mr Salmond said: "On the streets of Livingston, people have been asking why the chancellor has failed to do his part to limit the rapid rise in petrol and diesel costs.

"Every penny increase in the price of fuel at the pumps gives the chancellor an extra �20m in VAT revenues.

"This money could and should be put back into the pockets of motorists with a cut in fuel duties."

Mr Howard, who gave his support to candidate Mr Lindhurst during campaigning in Livingston town centre, told voters: "If you want Scotland to be part of the UK but you think it's heading in the wrong direction - and there are many things that show it is - the thing to do is vote Conservative next week."

Charles Dundas and his colleagues offered brooms to Labour

He said Mr Lindhurst was fighting a strong campaign on the future of St John's Hospital and law and order.

He highlighted the Tories' pledge of a review of the Human Rights Act, to be carried out by Lord Fraser.

"I don't want the Human Rights Act to be telling our courts who they can give bail to and who they can't," Mr Howard said.

The Scottish Lib Dems targeted labour on crime and focused on a pledge by Mr Devine to "clean up our streets", claiming this was an admission that his party colleagues on West Lothian Council were losing the crime fight.

A spokesman said: "Local Liberal Democrat Charles Dundas and his team have responded to this admission of failure by taking a set of new sweeping brooms along to the Labour's campaign headquarters so that Jim Devine can pass them on to his Labour colleagues in charge of the council."

Labour is defending a majority of more than 13,000 in Livingston in the 29 September poll, which has been caused by the death of former Foreign Secretary Robin Cook.