A Tory peer today warned his 16-year-old granddaughter, Katie, who lives near Peebles that she would become a foreigner, cut off from her family living in England, if Scotland votes for independence next week.

In a highly personal message to her, which he has decided to publish, Lord Cormack warned: "Much of the noise and ill-tempered debate of recent weeks seems to have obscured rather than illuminated the stark and simple fact: Do families like ours remain British or do those family members who live north of the border become citizens of a small country that is no longer a vital part of a great nation?"

He appealed to her: "You must now choose whether you remain British like your granny who was born in Aberdeen and me who was born in a family with deep Scottish roots, or whether you become a foreigner separated from us and from your cousins."

Lord Cormack said that no sensible person could possibly deny that Scotland could become a successful small country.

"The question for you is whether, if it does, your life will be richer and fuller and your prospects and opportunities greater and more exciting than if you remain British.

"As you enter your final school year, all the benefits and opportunities that come with being a citizen of a major power, to which Scotland and its people have contributed so much, lie before you."

He added: "I do hope you will think it is sensible that we should stay together."