David Cameron has pleaded with Scots not to vote for independence simply as a way of giving the "f-ing Tories" a kicking.
Speaking in Edinburgh on Wednesday morning, the prime minister said he would "heartbroken" if the UK was broken up on September 18.
"People can feel like it's a bit like a general election. That you make a decision and five years later you can make another decision. If you’re fed up with the f-ing Tories give them a kick and then maybe we'll think again. This is totally different," he said.
The Conservative Party only has one MP in Scotland. Alex Salmond has had some success in framing the debate as a chance for Scots to never again be governed by the Tories.
With the result on a knife edge, Cameron also insisted he would not step down as prime minister should Scotland choose independence.
In the event of a Yes vote, the pressure on the prime minister, having lost the Union, to quit, would be huge. But he insisted he would stick around to handle the separation negotiations.
Cameron, Nick Clegg and Ed Miliband are all in Scotland on separate visits in a bid to persuade Scots to vote No, offering instead a fast-tracked timetable for further devolution.
The prime minister acknowledged that the Conservatives would have a better chance of winning UK elections if the Labour stronghold of Scotland left, but insisted he did not care about that.
"I care far more about my country than I do about my party. I care hugely about this extraordinary country, this United Kingdom that we've built together," he said. "I would be heartbroken if this family of nations that we've put together was torn apart."