Tory leader David Cameron and former Ulster Unionist leader David Trimble teamed up to brand Labour out of touch on the Holyrood campaign trail.
David Cameron said a positive case for the union should be made
While visiting the Borders, Mr Cameron said Labour had attempted to "frighten" Scots into staying in the Union.
Fighting back, Scots Labour leader Jack McConnell said the Tories had a "talk tough, vote soft" attitude to crime as he visited the same part of Scotland.
Lord Trimble has become a Tory peer in the House of Lords.
Speaking in Gretna Green - a famous marriage venue - Mr Cameron said voters should be "inspired" by being offered a positive case for the Union.
In his first public speech at a Tory gathering, Lord Trimble said: "Scottish Labour is old Labour, out of touch and out of date and it doesn't have the solutions we need in public services and revitalising the economy."
"I can understand people in Scotland being fed up with Labour - but why turn to a party that in terms of its social and economic instincts is, if anything, further to the left?"
Lord Trimble added that the SNP did not want to see people content with the administration within the UK, saying: "They want to sow more discontent and more discord."
Mr Cameron, who was also accompanied by Scots Tory leader Annabel Goldie, denied his party would prop up a Labour-led Scottish Executive to keep the SNP out of power.
"Britain benefits from having Scotland and England with such strong Armed Forces," he said.
"Scotland punches above its weight in Britain's Armed Forces - and Britain punches above its weight in the world."
Mr McConnell claimed that crime peaked in Scotland in 1991 under the last Conservative government, when crime doubled and violent crime rose by 170%.
He said the number of police officers was cut in the Tories' last years in office.
Jack McConnell discussed plans to increase community wardens
Mr McConnell joined Justice Minister Cathy Jamieson in Dumfries to discuss plans to double the number of community wardens in Scotland to more than 1,000.
"David Cameron would rather hug hoodies than back tough action on anti-social behaviour," he said.
"But there is a chance for him and for the Tories in Scotland to prove that they are serious about law and order."
Labour said the Tories had shown their "talk tough, vote soft" attitude by opposing control orders, 90-day detention powers, tougher jail sentences and a commitment to scrap ID cards at Westminster.
Labour also said Conservative MSPs had voted against legislation to protect emergency workers and the Custodial Sentences and Weapons Act.
An SNP spokesman said it was committed to making Scotland more successful in order to prove itself in government before holding a referendum on independence in 2010.
"That's why we have been working hard to set out our range of positive policy proposals throughout this campaign so that we can take Scotland forward to a successful future," he added.