Annabel Goldie yesterday launched a vehement defence of the Union but refused to commit her party's support for an anti-Nationalist coalition to defeat the SNP's plans for independence.

In a keynote speech in Edinburgh, the Scottish Conservatives leader said Scotland was currently able to "shape the world" through the UK's membership of Nato, the G8 and the UN Security Council - all of which independence would put under threat.

She predicted that there would be "a clear Unionist majority" in the Scottish Parliament after May 3, with the Tories, Labour and the Liberal Democrats taking most of the seats. But she stopped short of pledging to join forces with Labour and the LibDems to secure an anti-independence majority at Holyrood.

The Tory leader said: "I have indicated that whatever regime seeks to form a legislative administration in the Scottish parliament, I and the Scottish Conservatives will not enter into coalition with them.

"We will look at the best interests of Scotland by considering what that administration seeks to put forward on an issue by issue basis."

Ms Goldie said Jack McConnell and Nicol Stephen posed "an equally serious threat" to the Union as Alex Salmond and the SNP.

"Their incompetence in running the country has made Scotland question devolution. Their failure has made Scotland doubt its future.

"And their lack of vision has led some Scots to wonder whether we should tread a different path."

Ms Goldie was particularly scathing in her assessment of Mr Stephen, whose party could be the SNP's coalition partners after the election. She said the LibDem leader was "willing to betray the Union by supporting the separatists".