Mr Brown was campaigning with wife Sarah in Kirkcaldy and Cowdenbeath
Gordon Brown has been on the campaign trail in his Kirkcaldy and Cowdenbeath constituency with his wife Sarah.
The prime minister was heckled by the SNP's Keith Brown, the Scottish schools minister, when he visited his street.
The first weekend of official campaigning in the run up to the 6 May election also saw Alex Salmond out spearheading the SNP's efforts.
The Conservatives are focusing on the economy, while the Lib Dems are detailing their plans for the elderly.
Mr Brown said he had travelled to Scotland just days after calling the general election "because what happens here directly affects who will form the next government at Westminster".
He added: "The choice across Britain is the same, from John O'Groat's to Land's End: Labour or Conservative. As Jim Murphy and Iain Gray have rightly said, it is a two horse race.
"It is a choice between help for families and support for our frontline public services, and an economic policy that is so flimsy it exists only on a press release."
Meanwhile, the Tories' Scottish campaign manager, David McLetchie, was out in Edinburgh highlighting his party's plans to rebuild the economy.
He said: "Scotland has been battered by the economic storm created by Labour's recession."
Mr McLetchie pointed out that unemployment was still rising north of the border, despite the falling jobless total across the UK.
"Business failures are rising in Scotland but falling in England," he said.
"We can't go on like this."
SNP leader Alex Salmond teamed up with Richard Thomson, the SNP candidate for Gordon, on a visit to a filling station in Huntly, where the first minister highlighted the rising price of fuel.
He said: "Rocketing prices are disastrous for the rural economies such as Gordon where a car is not a luxury - it's a necessity.
"Here in Huntly, prices at already edging above £1.20 and in some parts of Scotland a litre of fuel is almost £1.30.
"Filling up a family car now costs the best part of £100."
The Liberal Democrats are focusing on their plans for the elderly, pledging to restore the link between earnings and pensions.
Danny Alexander, the party's candidate for Inverness, Nairn, Badenoch and Strathspey, said: "In the election, the country has a choice about the way forward.
"By voting for the Liberal Democrats, we can face those decisions honestly and choose to build a fairer country."
He also pledged more help with fuel bills, adding: "We will make sure that the winter fuel payment is given to severely disabled people, and families with disabled children who are among the most likely to face the misery of fuel poverty."