David Cameron has stressed he will work to ensure the Scottish National Party (SNP) does not succeed in 'splitting up' the UK.
While the Scottish Tories recently endorsed the Nationalists' budget plans for the coming year, Mr Cameron said co-operation between rival parties would not extend to condoning Scottish independence.
However, the Conservative party leader praised the 16 Conservative MSPs who voted for the £33 billion budget proposals.
He added: "Our support for this budget will in no way diminish our vigorous opposition to the SNP and what it represents.
"If elected, I will do everything in my power to ensure the SNP will not be able to split up the UK.
"I want to be a prime minister of the whole United Kingdom. That's not because I'm some kind of megalomaniac, it's because we have so much in common and we have done so much together."
The Conservative leader, who yesterday pledged to send his children to state secondary schools, said the UK government needed to examine its relationship with the Holyrood administration.
"If we win the next election at Westminster, we would govern with a maturity and a respect for the Scottish people," Mr Cameron added.
"I would be a prime minister that would work constructively with any administration at Holyrood for the good of Scotland and I would be in regular contact with the first minister, no matter what party he or she came from."