Gordon Brown will this week spearhead an attempt by opponents of Scottish independence to regain the momentum by warning the country would face a £1.5bn pensions and benefits black hole if it breaks away from the United Kingdom.
His intervention comes amid evidence that support for separation is growing ahead of the independence referendum on 18 September. One poll on Sunday suggested a swing of just two points could be enough to secure a Yes vote.
The former Labour Prime Minister will argue that Scotland receives £9.6bn in pensions and benefits annually – £500m more than the amount it should get if the payment was based on the size of its population.
He will also claim it would cost the country £1bn to establish its own pensions system if it separated from the UK.
Mr Brown said: “I will not be setting out the Tory case for Britain. I will set out a positive, forward-looking case for the best future for Scotland, showing how in areas such as pensions it makes good sense to combine having a Scottish parliament with being part of Britain.”
He will be speaking for the first time for the Better Together campaign, which is led by the former Labour Chancellor Alistair Darling.
The campaign has come under fire for its tactics as the polls showed a narrowing in the gap between the pro- and anti-independence camps.
An ICM poll for the Scotland on Sunday newspaper showed support for independence at 39 per cent, while opposition had fallen by four points to 42 per cent. The results put Yes on 48 per cent and No on 52 per cent.
The Yes Scotland campaign said the tide was moving in its favour. Blair Jenkins, its chief executive, said: “The extreme negativity of the No campaign is proving a major turn-off for voters.”
The Labour leader, Ed Miliband, will hold a shadow Cabinet meeting in Glasgow this week, as well as staging a public meeting in the area. Campaigners believe that working-class Labour-leaning voters in central Scotland could hold the key to the referendum’s outcome.
Mr Miliband’s main task is to persuade them that their best chance of social justice is within a Labour-led UK rather than a breakaway state.
Margaret Curran, the shadow Scottish Secretary, said: “We will show it’s only Labour that has the positive, progressive vision to take Scotland forward.”
Scotland’s Deputy First Minister, Nicola Sturgeon, ridiculed Mr Brown’s claim on pensions and said an independent Scotland was better placed to afford pensions and welfare than the UK.
She said: “The last person anyone in Scotland will take lessons from when it comes to pensions is Gordon Brown – the man who destroyed final-salary pension schemes with his £100bn raid, and insulted our older folk with a miserly 75p increase in the state pension. His track record means he lacks all credibility.”