The SNP outspent Labour in Scotland by more than £1m during its successful campaign for government last year, official figures showed last night.

The data from the Electoral Commission also revealed how the grassroot popularity of the Nationalists is growing exponentially with membership rising from just 9458 in 2003 to 13,944 in 2007, an increase of almost 50%.

This, coupled with increased subscription charges, boosted income from membership over the same period from £54,147 to £310,805.

Yesterday, Angus Robertson, the SNP's leader at Westminster, pointed out that the Glasgow East by-election victory had already attracted more than 250 new members, pushing total membership above 14,000.

The party's accounts revealed how the average age of an SNP member was 53 with a quarter over 65. The number of donors giving less than £200 rose from 2713 in 2004 to 10,407 in 2007 while the number giving over £50,000 during the same period rose from four to 26. Brian Souter, the Stagecoach chief, famously gave the Nationalists £500,000 ahead of the May 2007 election.

The SNP's books revealed it spent £1,676,223 on campaigns last year compared to Scottish Labour's £638,014.

The Conservatives, meantime, spent £598,000 fighting last year's Holyrood election while the Scottish Liberal Democrats spent £278,000 on elections, most of which went on the Scottish parliamentary poll.

Overall last year, the SNP received £2,562,970 and spent £2,803,560, producing an annual deficit of £240,590. The accounts also showed it owed its creditors more than £800,000.

Scottish Labour's income was £1,029,358 while its expenditure was £940,851, creating a surplus of £88,507.

The Scottish Liberal Democrats raised £691,055 and spent £766,038, producing a deficit of £74,983. The Scottish Tories do not produce separate accounts.

UK-wide, Labour last year cut its overall debt from £25m to £18.9m while Jack Dromey, its treasurer, said a "new discipline" and a "determination to live within its means" led to a £7.5m surplus for 2007.

Tony Blair's decision to take on massive loans from wealthy supporters to fund the 2005 General Election campaign continues to limit the room for manoeuvre of his successor as Labour leader. Gordon Brown recently announced that the party was scrapping its 2009 spring conference in what was widely seen as a cash-saving measure.

Despite paying off an £854,000 loan from biotech tycoon Sir Christopher Evans and partially repaying a loan from software millionaire Gordon Crawford over the course of 2007, Labour still owes more than £15m to individual lenders. Interest on the loans reached more than £1.5m by the end of last year.

Mr Dromey stated in the accounts: "We recognise that, despite the progress that has been made, significant problems remain. We have a big job to do in the period ahead, therefore, to put the party on a firm financial footing for the future."

Caroline Spelman, the Conservative Chairwoman, said Labour's financial position put it "in hock to the unions", which funded the party to the tune of around £10m last year and provided more than 90% of its donations in the first three months of this year.

"These accounts highlight the extent to which Labour is in hock to the unions. Mired in debt, Gordon Brown and the Labour Party have only been able to stave off bankruptcy by doing deals with union barons," insisted Ms Spelman.

The Tories' accounts showed a reduction in debt from £9m to £7.75m in 2007, when the party recorded a surplus of around £1.5m down from £4.2m.

Liberal Democrat books showed the party had a deficit of around £350,000 in 2007 but remained in the black to the tune of almost £1.3m.

The LibDems' healthy finances are due in large part to a £2.4m donation in 2005 from Michael Brown, the Glaswegian tycoon, who went on the run this week ahead of his scheduled trial on fraud and money laundering charges.

The party has consistently said it will not return the money, which it insists was accepted in good faith and registered with the Commission in line with funding rules.

However, the watchdog has yet to give its final ruling. If it were to find against Nick Clegg's party, then the Liberal Democrats would have to give up the £2.4m, which could mean a levy on members to raise the money.

By law, the cash would not go back to Brown the donor but the Consolidated Fund - the UK Government's bank account.