David Cameron accused others of ignoring bread and butter issues

Speaking in Edinburgh, he accused Labour of using "bone-chilling" language to frighten Scots.

Mr Cameron said Scots wanted to see bread and butter issues like housing, health, education and crime debated.

Labour said it was right to highlight a potential threat to the Union, while the SNP called for a "fresh" approach.

Mr Cameron, who was joined by Scots Tory leader Annabel Goldie, said Labour and the SNP were wrong to fight the Scottish election campaign on constitutional issues, adding that Scottish voters did not want to be "bullied" into staying in the Union.

The Tories and Labour are two sides of the same London coin Angus Robertson, SNP Read the election weblog

He said of Labour's campaign strategy: "They aren't talking about the bread and butter issues because there has been a shortage of bread and a shortage of butter and they have got so many weaknesses on those issues.

"I also think they are making a mistake in some of the bone-chilling language they are using."

The main theme of the Tory campaign has been dubbed "Your Voice in Parliament", featuring commitments to tackling drugs and crime, as well as providing affordable housing.

Further pledges also aim to help the families, including the extension of free nursery provision.

Tony Blair and Jack McConnell backed the United Kingdom

Mr Cameron's visit came as First Minister Jack McConnell travelled to London to endorse a partnership agreement with Tony Blair on policy co-operation.

Labour's Holyrood campaign chair, Cathy Jamieson, said Mr Cameron had only expressed "warm words and empty rhetoric" during his visits to Scotland.

She added: "The Tories need to recognise that their policy-light campaign could allow Scotland to sleep-walk into an expensive separation of Scotland from the rest of the UK - a separation that would cost Scottish families over �5,000 more with the SNP."

SNP campaign manager Angus Robertson said: "Scotland needs a fresh approach, with a successful SNP government delivering our positive policies to lower class sizes, keep healthcare local, and reduce crime.

"The Tories and Labour are two sides of the same London coin. Labour are indeed running an extreme and negative scaremongering campaign against the SNP but they have taken their template from the Tories."

Scottish Liberal Democrat election director Tavish Scott said the Conservatives had become irrelevant north of the border.