The unionist parties are poised to offer Scots new powers within days amid widespread alarm at Westminster over the rise in support for independence.
Within hours of a new poll putting the Yes campaign ahead in the race for the first time, Chancellor George Osborne announced that plans for further devolution to Holyrood would be accelerated.
New details are expected to be published this week on the timetable and process for the transfer, and a commitment is due on establishing a convention after a No vote to try to build a consensus on the way forward.
Former Prime Minister Gordon Brown predicted that when voters were aware of the proposals – expected to include tax, spending and welfare powers – they would opt for enhanced devolution over independence.
However, some commentators questioned why the pro-UK side had fought so hard to keep the “devo max” option off the ballot paper in the first place.
First Minister Alex Salmond branded the move a “bribe”.
More than 100 English and Welsh MPs – mainly Labour – are expected to travel north this week and next as the battle over Scotland’s future goes down to the wire.
Mr Osborne said: “You will see in the next few days a plan of action to give more powers to Scotland. More tax powers, more spending powers, more plans for powers over the welfare state.
“That will be put into effect – the timetable for delivering that will be put into effect the moment there is a No vote in the referendum.
“The clock will be ticking for delivering those powers, and then Scotland will have the best of both worlds.”
Mr Brown said last week that he had asked the Speaker at Westminster to dedicate the first available time slot in the Commons after the referendum to the devolution process.
“I think when people see the full scale of the powers the Scottish Parliament will have, and our ability to do things while retaining the benefits of the UK, including the currency, I think they are going to decide on the extended powers of the Scottish Parliament within the UK,” he said.
Mr Salmond, the SNP leader, dismissed the move, asking: “Are we expected to believe, after hundreds of thousands have already voted, that there’s a radical new deal?”
He added: “This is a panicky measure made because the Yes side is winning on the ground.”
“They’re trying to bribe us, but it won’t work as they have no credibility left.”