Prime Minister David Cameron urged people in all parts of the United Kingdom to persuade their Scottish friends and family to vote against independence in September's referendum.
In an impassioned speech in London on Friday, Cameron warned there were "seven months to save the most extraordinary country in history", ahead of the September 18 vote which threatens to break up the UK.
Only four million Scots can vote, but the British leader reached out to the 59 million people in England, Wales and Northern Ireland, which he said would be "deeply diminished without Scotland".
"Get on the phone, get together, email, tweet, speak, let the message ring out... We want you to stay," Cameron said.
"You don't have a vote, but you do have a voice. Those voting are our friends, neighbours and family. You do have an influence."
Cameron, whose Conservative party has only one member of parliament in Scotland, held up his own Scottish roots, saying his surname stems from the West Highlands.
"The name Cameron might mean 'crooked nose' but the clan motto is 'Let us unite' - and that's exactly what we in these islands have done," the prime minister said.
Polls show increasing support for the Yes campaign, led by the Scottish National Party (SNP) in power in Edinburgh - although the No vote remains ahead - and Cameron said there could be "no complacency".
He delivered his speech at the site of the London 2012 Olympic Games, on the opening day of the Sochi Winter Games, and highlighted how all parts of the UK pulled together behind "Team GB" during the sporting contest.
Citing also the global clout, the economic benefits and the shared history and values of the UK "family", Cameron said: "We come as a brand - a powerful brand.
"If we lost Scotland, if the UK changed, we would rip the rug from under our own reputation. The plain fact is we matter more in the world together."
