Ex-PM says Scotland Act would set new rate of income tax and boost borrowing powers for parliament if independence bid fails

Gordon Brown has written to the House of Commons' speaker requesting several days of parliamentary time to debate further devolution measures for Scotland.

In a move designed to reassure Scottish Labour supporters who are considering voting for independence in 13 days, the former prime minister asked John Bercow to ensure time is set aside when parliament returns in October in the event of a no vote.

The yes campaign has experienced a late surge in support for independence, while some nationalists have questioned how serious Labour is about devolution.

It is widely believed that Alex Salmond's government has successfully argued that the referendum is a protest vote against the Tories, lifting the yes vote to within three percentage points of a win, according to the pollsters YouGov and Survation.

Speculation is growing that a survey this weekend will show a significant lead for the yes campaign for the first time.

In another indication of Labour's concerns, the party's leader, Ed Miliband, met with the Scottish parliamentary Labour party on Friday and pledged that 100 of the its MPs would campaign north of the border in the runup to the vote.

Brown told the meeting in Westminster on Friday that he planned to use parliamentary time to lead the discussion over the process and schedule for further powers, including tax-raising powers, to be transferred to Holyrood.

"Scotland must make its choice, but Westminster must play its part too. So I can say that I will personally seek to lead a debate on the floor of the House of Commons in the first week that Westminster returns after the referendum, with the specific aim of confirming the public and well-understood agreement on the process and timetable for further devolution."

At the meeting of the Labour pressure group Progress, Brown said the Liberal Democrats and the Tories were committed to reforms. "I have already written to the Speaker of the House of Commons, asking him to recognise the significance of this matter by setting aside time in the first days back for me to put the case. This way there can be no doubt of the strength of the UK parliament's commitment to change and no going back on the promise of further legislation," he said.

Seeking to cut off the argument by some independence supporters that Westminster's promises could easily be broken, Brown sought to reassure the Scottish electorate that this would not happen.

"This is not like the 1979 referendum, when promises made were reneged upon," he said. "This is instead akin to 1997, after which Labour's promise of a Scottish parliament was immediately delivered, and to 2012, when the recommendations of the Calman commission, which started out with our government were then quickly enshrined in law with cross-party support and the agreement of the Scottish parliament."

He said the Scotland Act would establish a new rate of income tax, devolve stamp duty and create borrowing powers for the Scottish parliament. He said he expected to see other tax-raising measures, benefit levels and powers over transport handed to Holyrood.

Brown also warned that an independent Scotland which kept the pound would be in a "colonial" relationship with the rest of the UK.