ALEX Salmond has accused his opponents of stoking up fears about immigration to attack the case for Scottish independence.

Writing in The Herald today, the First Minister accuses Labour, the Conservatives and Liberal Democrats of using the issue of immigration as a "weapon" in the referendum fight.

Last week he said an independent Scotland under the SNP would seek to attract an extra 24,000 people per year to live and work in the country as part of a series of measures to boost tax revenues by £5 billion by 2030.

He explained the figure was only 2000 above the average annual net migration of 22,000 between 2001 and 2011.

However, this period coincided with high levels of immigration from new EU countries such as Poland, whose citizens gained the right to live in Scotland.

The UK Treasury has estimated Scotland's long-term average annual net migration at 15,500.

Mr Salmond writes: "The main Westminster parties have decided to deploy immigration as a weapon in their increasingly tawdry self-styled 'Project Fear' campaign." He claims the Coalition Government and Labour have highlighted the net migration figure "as if it were something to be frightened of; a reason to vote No".

The FM also accuses the three Better Together parties of copying Ukip's tactic of "engendering fear" of migration as part of the referendum campaign.

He said: "We can jettison the aggressive language of the mainstream Westminster parties, who instead of standing up to the likes of Ukip have decided to pander to them."

He adds: "In modern Scotland we should aspire to be a beacon of hope, diversity and humanity."

His comments follow a recent poll by Dundee University, where the SNP leader is due to speak tonight, which suggested that almost seven out of 10 Scots back the Ukip policy of stricter immigration controls.

Pollsters who questioned 1000 Scots over 16 for a university project found that most believed benefits should only be available to UK residents of at least five years.

The First Minister's broadside comes as David Cameron signalled that more powers for Holyrood could arrive soon after the 2015 General Election now that the Scottish Conservatives had proposed giving full control over income tax to the Scottish Parliament in the event of a No vote .

Ruth Davidson, the Scottish Conservative leader, yesterday insisted her party's new proposals to hand over all powers on income tax to Holyrood would produce "a more powerful Scottish Parliament, a more responsible Scottish Parliament".

The Prime Minister said the Tory Strathclyde Commission into further powers for Holyrood had produced a "clear, coherent and Conservative blueprint for the next stage of Scotland's devolution journey".

But deputy First Minister Nicola Sturgeon urged Scots to shun the "desperate bidding war from the Unionist parties" and vote Yes to guarantee all powers went to Holyrood.

Last night, an Ipsos Mori poll showed of those certain to vote in the referendum, 36% backed a Yes vote, up four points since March, while 54% supported a No vote, down three. Without don't knows, the split is 40% Yes, 60% No.

Meanwhile, Business for New Europe, a coalition of pro-European business leaders, has said an independent Scotland would not become a full member of the EU until 2019.