GORDON BROWN hit the campaign trail with his wife Sarah yesterday as he announced a six-day, 30-stop tour of Scotland as part of the final push for a No vote.

The former Prime Minister, who campaigned in his Kirkcaldy constituency yesterday, will speak at a rally in Midlothian today with Johann Lamont in which he will discuss his proposals for more economic, fiscal and social policy devolution.

He will question the SNP's proposals on the economy, including currency, public spending and employment.

He will say: "There are five challenges that the SNP have not faced up to: more jobs - 1.4 million - linked to foreign ownership and exports than most countries; banks 12 times the size of an independent Scotland's national income; a £6 billion public spending hole when we lose the Barnett formula and the UK welfare state; and the uncertainty over the currency as well as the SNP's threat to renege on our share of the debts. The truth is Scots would be entering an economic minefield under the SNP's economic plans for separation. While it is already well known Mr Salmond has no Plan B for the currency, it is now clear he does not have a Plan A."

He will warn that the SNP's "threat to default on their debts will explode in their faces".

"When 70 per cent of our trade is with the rest of the UK and most of our R&D is financed by it, default on our share of the UK's debt will mean not just higher interest rates for mortgages and businesses, and a reduction in lending, but also lost jobs," he will say.

Writing in a Sunday newspaper, he acknowledged that the referendum battle was proving tougher than some had expected - and laid the blame squarely on the Tories.

"Why has it been difficult to win Scottish votes in support of this principle of sharing that most Scots hold dear?" the Labour MP for Kirkcaldy and Cowdenbeath wrote. "Many are angry that the bedroom tax was imposed upon Scots against their will while at the same time the very wealthy received tax cuts. The SNP also claim that the ramifications of any Tory privatisation of the NHS in England will cut budgets in Scotland.

"But English and Welsh people have already given an answer to the SNP claims.

"The answer is that 90 per cent of English people want to keep the NHS public and retain it free at the point of need."