The British government is scrambling to respond to a lurch in the opinion polls towards a vote for Scottish independence this month by promising a range of new powers for Scotland if it chooses to stay within the United Kingdom.

British finance minister George Osborne said yesterday that plans would be set out in the coming days to give Scotland more autonomy on tax, spending and welfare if Scots vote against independence in a historic referendum on September 18.

Prime Minister David Cameron had, ironically, vetoed a third ballot option for greater devolution, betting that the stark choice of yes or no to independence would deliver a clear victory for the status quo as cautious voters turned away from an uncertain future.

That looked like a precarious calculation after a YouGov poll for the Sunday Times showed supporters of independence had taken their first opinion poll lead since the referendum campaign began.

“You will see in the next few days a plan of action to give more powers to Scotland . Then Scotland will have the best of both worlds. They will both avoid the risks of separation but have more control over their own destiny, which is where I think many Scots want to be,” Osborne told the BBC.

British government ready to give Scotland more autonomy on tax, spending and welfare

“More tax-raising powers, much greater fiscal autonomy, more control over public expenditure, more control over welfare rates and a host of other changes.”

Osborne said the changes, being agreed by all three major parties in the British Parliament, would be put into effect the moment there was a ‘no’ vote in the referendum. His comments echo those of former British Prime Minister and opposition Labour party lawmaker Gordon Brown, who said on Friday he would spearhead a push for Scotland to gain more powers if it voted against independence.

All three major British political parties have already set out differing proposals on extra powers for Scotland if it rejects independence. Former finance minister Alistair Darling, who is leading the pro-union Better Together campaign, said the upcoming plans would not go beyond these.

“What is being announced this week is simply the timetable, the procedure for implementing them, which I think people will want to know,” Darling told Sky news.

Scotland already enjoys a large measure of devolution, having had its own Parliament since 1999 with the power to legislate in policy areas such as education, health, the environment, housing and justice.