Labour's Holyrood leader Wendy Alexander yesterday increased the pace on her new-found enthusiasm for a straight yes or no independence referendum, telling Alex Salmond: "Enough of huff, puff and bluff - bring it on."

But if Ms Alexander's uncharacteristically aggressive response was calculated to strike fear in her Nationalist opponents and inspire confidence in her party colleagues and Unionist allies, there was little sign of that working last night.

Her dramatic U-turn on television on Sunday came out of the blue, but she showed no sign of holding back on radio last night, saying the SNP's plans not to legislate until 2010 meant a climate of uncertainty right through to the next Holyrood election.

Arguing for a straight argument for or against independence, she said: "Let's get on with it. It's a measure of their weakness that all they do is bleat about me changing my mind. That will be forgotten by tomorrow. The reality is that the SNP are running scared of Scotland's verdict."

But Ms Alexander asserted that only now had the SNP said they would delay legislating for a referendum until 2010, when in fact that was their manifesto commitment.

She also said it would take nine months for that legislation to be passed, a claim the government denies, and she also cited business tycoon Sir Tom Hunter as calling for an early vote, something he specifically denied after comments he made recently.

Ms Alexander avoided the question of whether or not she had Gordon Brown's backing for the new tactic but she insisted: "I am very attracted to the idea of a straight choice for or against independence which Alex Salmond says he is in favour of but which he seems to be remarkably reluctant to put to the vote."

An aide to Deputy First Minister Nicola Sturgeon said: "We are delighted that Labour's disarray has forced Ms Alexander into a massive U-turn. We will stick to what we offered the people; demonstrating credibility in government, engaging with the people through our national conversation and bringing forward a referendum in 2010. This is a timetable that was set out in our manifesto."

Robert Brown of the Liberal Democrats, said: "This is a panic response from a Labour Party in free-fall after last week's English and Welsh elections. Wendy Alexander does not support independence and politicians should not support a referendum which they do not back.Voters in Scotland will not look kindly on politicians who put themselves and their party above the interests of the country."

A Tory spokesman said: "Scotland's future should be the subject of calm and considered debate, not knee-jerk panic by a Labour Party in political meltdown. The Calman Commission should be left to get on with its health check on devolution."