The high-profile campaign, called Let’s Stay Together, invites people who may not have a vote in the referendum, but care about the outcome, to express their belief in the UK and their affection for Scotland.
The group is led by Andrew McGuinness, the founder of BMB and Seven Dials, and Scots born MT Rainey (founder of Rainey Kelly Campbell Roalfe/Y&R and the chairman of Th_nk) and is supported by a number of high-profile industry figures and agencies.
The campaign will encourage people from England, Wales and Northern Ireland to lend their voice to the "let’s stay together" message by adding their name to the dedicated website.
The online launch film, named "Scotland, you're my best friend" and set to Queen’s 'You’re My Best Friend' features a host of celebrities from Richard Wilson to Ross Kemp. It was directed by Nathan Sam Long through Silverfish Media. The producer was Mark Lucas.
The campaign is separate from Better Together, the cross-party push to get Scottish residents to vote no to independence, which hired M&C Saatchi in June.
McGuinness said: "This a campaign to let the Scots know that we want them to stay with us. We want people who have a vote to know that people elsewhere in the UK care deeply about Scotland and want us to stay together."
Rainey said: "As a Scot in London, I can’t vote, so I’ve done what I can do to help to inspire and assemble this campaign. I hope it gives a voice to all of us who want to express how much we value the UK and Scotland’s role within it."
Further activities are planned between now and the referendum on 18 September.
The campaign is also on twitter (@wakeuptobreakup and #letsstaytogether) and facebook at www.facebook.com/letsstaytogethercampaign. There is a playlist of emotional anthems on Spotify.
The website has been developed by Th_nk, the digital agency that works with clients including Britvic, whose digital business it picked up earlier this year.