David Cameron is "taking a gamble" on the future of the UK by allowing the referendum on Scottish independence, a Tory Party heavyweight has said.
Ken Clarke, who first became a Tory minister in 1972 when Cameron was six, has criticised the September 18 poll to decide whether to end the UK in its current form, saying the issue is too important for a one-day vote.
In an interview with The Sunday Telegraph, Clarke said: "Referenda are always a gamble."
Ken Clarke said the referendum 'risked the future of the United Kingdom'
"To have big complicated questions decided by one vote on one day is not as good as a continuous process of parliamentary debate," the long-term minister said.
"Having risked the future of the United Kingdom, I trust that the good sense of the Scottish people will keep it together.
"To try to take it on and try to settle it is fine.
"But it is a pity that the whole issue has been allowed to get to a pitch where we are effectively taking a gamble on an opinion poll taken on one day with the whole future of the United Kingdom."
He said it would "revive the medieval state of Scotland and start disentangling the closely intertwined peoples and economies of Britain and Scotland in some as yet unplanned and unknown way".
The SNP described this remark as "offensive". Clarke also said a no vote would be essential to maintain Tory momentum going into the 2015 General Election.