A former Tory Prime Minister has claimed holding two more referenda on independence could help safeguard the Union.
Sir John Major said a final vote could be staged on the outcome of the negotiations after an initial referendum on the principle.
After being rejected by the voters in 2014, recent opinion polls have shown independence to be in the lead.
If a pro-independence majority of MSPs is returned at the next Holyrood election, First Minister Nicola Sturgeon is expected to demand indyref2.
However, the Tory Government is refusing another referendum, with Scottish Secretary Alister Jack claiming it could be 40 years before another one is held.
Major, who was PM between 1990 and 1997, has suggested the pro-UK side take another approach.
In a lecture, he said “one deeply troubling effect” of Brexit is the risk posed to the UK, with Scotland “most likely to leave”.
He said: “To keep the Union together will require consensus, consideration and consultation.
“The Government must engage, coax, encourage, and examine every possible route to find an arrangement that will obtain a majority for union.”
Arguing that refusing another referendum might “help the separatist case”, he said:
“The choice for the UK Government is either to agree the referendum can take place – or to refuse to permit it. Both options come with great risk. But the lessons of Brexit may offer a way ahead.
“The Westminster Government could agree for an Independence Referendum to take place, on the basis of two referenda. The first to vote upon the principle of negotiations, and the second upon the outcome of them.
He added: “The purpose of the second referendum would be that Scottish electors would know what they were voting for, and be able to compare it to what they now have. This did not happen with Brexit: had it done so, there may have been no Brexit.
“Many Scottish voices – and especially business – may support the logic of this: it may focus minds away from a short-term reflex opposition to a perceived English Government, and back to the mutual and long-term virtues of the Union.”
