The Prime Minister today hit the by-election campaign trail for the second time in less than a week with a return visit to Glenrothes.
He did so as bookies cut the odds against Labour holding the seat, now putting them on even money while the SNP have moved to 8/11.
But the visit also came against the backdrop of a row over the Lloyds TSB-HBOS bank merger, with a Scottish financial figure accusing Mr Brown and the Chancellor of trying to "railroad" the merger through.
The campaign got off to a low-key start with a visit to the UK headquarters of window manufacturer Velux, which employs 450 in Glenrothes.
But the temperature was due to rise later on with an attack on the SNP.
Ahead of a private visit to the Brand-REX plant, owned by entrepreneur David Murray, which supplies cables to the MoD, Mr Brown said: "Labour knows Scotland is stronger as part of the UK.
"The SNP's commitment to divorce Scotland from the UK would put too many jobs at risk like those at the Brand-REX factory I am visiting."
During his visit to the Velux plant Mr Brown was accompanied by Labour candidate Lindsay Roy, 59, a local headteacher.
The Prime Minister and Mr Roy toured work stations in the company's contact centre.
The Danish-owned family firm makes roof lights and solar panels, and Mr Brown disclosed he had a solar panel at his home in North Queensferry.
He extolled Mr Roy to the assembled employees.
"We fought for this by-election to replace John MacDougall, an excellent Member of Parliament and very good friend of mine, we wanted someone who was not an ordinary politician," he said.
"Lindsay, as a head teacher, has huge experience of how to deal with anti-social behaviour, helping young people realise their potential, helping young people into jobs.
"That is why we chose him as a candidate - to send a different message about what can be achieved for the future."
The Prime Minister continued: "Our task at the moment, given that we have this huge set of global problems that we are trying to deal with, is to help people fairly through these difficult times and to do everything it takes to get our economy moving forward again.
"That's why I've tried to persuade the rest of the world to do some of the things we have done.
"That is why we also need people in Parliament to speak up for the concerns and needs in every community of this constituency."
Mr Brown joked that when he first became an MP in Fife in 1983, his election manifesto had emphasised the need to elect an MP with youth and fresh ideas.
"At the last election I put on my manifesto this constituency needs a Member of Parliament with maturity."
Today's visit came six days after Mr Brown paid his first campaign visit to Glenrothes, breaking with several years of Prime Ministerial tradition.
Tony Blair did not take part in by-elections after 1997, and initially this tradition was cited to explain Mr Brown's absence from Glasgow East and later the early stages of the Glenrothes campaign.
Today's visit ran the risk of being overshadowed by the row over the Lloyds TSB HBOS merger.
The accusation that Mr Brown and the Chancellor were trying to "railroad" the merger through came from Jim Spowart, founder of Intelligent Finance, who said today: "A merger with Lloyds TSB is not the best option.
"And with thousands of jobs in the balance I implore Mr Brown to think again."
Mr Spowart said the banking sector rescue package which took place after the initial merger announcement had changed the circumstances, and that HBOS could have a future on its own.
Mr Spowart, who signed an open letter in support of Labour in the 2007 Scottish election, said: "If a Labour Government presides over the decimation of the Scottish banking sector and the virtual disappearance of our oldest bank, it will cause a lot of people to question what the point of the union is."
Meanwhile, reports today suggested most of the top jobs in a merged Lloyds TSB and HBOS would go to Lloyds TSB executives, with only a few going to executives of HBOS or the Bank of Scotland.
The Glenrothes by-election, in which voters go the polls on Thursday, was caused by the death of John MacDougall, who had a majority over the SNP of 10,664 at the last general election.
At first the election was seen as utterly critical to the political future for Mr Brown after Labour's spectacular loss of Glasgow East to the SNP, but the contest has since been overshadowed by the world's economic woes.Reuse content