In a much hoped for intervention by politicians in Westminster, the Queen told well-wishers outside church in Aberdeenshire in Scotland yesterday: "Well, I hope people will think very carefully about the future".
It is the first time she has spoken directly on the historic referendum and follows calls from Unionists for her to speak out in favour of a 'no' vote.
Last week, Buckingham Palace had warned politicians not to drag her into the battle, after both Labour and Conservative backbenchers urged her to intervene.
Meanwhile, Scottish First Minister Alex Salmond and British Prime Minister David Cameron are due to hit the Scottish campaign trail ahead of Thursday's yes or no vote.
More From This Section
Salmond is to join business leaders to argue that a "Yes" vote would help to grow Scotland's economy.
Cameron will be in Scotland to give a speech arguing there are strong "head and heart" reasons to vote "No".
Meanwhile, popular English footballer David Beckham has backed the "No" campaign, urging a vote to renew the UK's "historic bond".
"What unites us is much greater than what divides us. Let's stay together," he said in an open letter released by the Better Together campaign.