The leaders of Britain's three main political parties - David Cameron, Ed Miliband and Nick Clegg - have rushed to Scotland to try to persuade voters to stay in the United Kingdom.
The three leaders have backed a plan of action for boosting the Scottish Parliament's powers if voters reject independence. They said the timetable would see work begin on the handover of new powers on 19 September, the day after the referendum.
Mr Cameron and Mr Miliband abandoned their usual Prime Minister's Questions session in the House of Commons to head north, after recent opinion polls suggested the referendum race was now neck and neck.
A new poll, by Survation for the Daily Record, conducted before the Westminster party leaders announced their campaign visits, has suggested 47.6% of voters back "No", 42.4% "Yes", with 10% undecided.
Although the three leaders campaigned separately, they each called on voters to keep Scotland in the United Kingdom.
Speaking in Edinburgh, Mr Cameron said the referendum result was irreversible, adding: "Because it's a ballot, I think people can feel 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 effing Tories, give them a kick and maybe we'll think again.
"This is totally different to a general election. This is a decision about not the next five years, it's a decision about the next century."
The prime minister said he was often asked whether his party would find it easier to win UK elections without Scotland, which currently has one Tory MP.
He responded: "My answer to that is, 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.
"I would be heartbroken if this family of nations that we've put together - and we've done such amazing things together - if this family of nations was torn apart."