'We will win.' Alistair Darling claims victory is in sight for no vote

Alistair Darling all but declared victory for the no campaign ahead of Thursday's historic referendum on Scottish independence on Saturday as an opinion poll for the Observer showed Better Together had seized back the lead.

In a remarkable show of confidence following a week of panic in the no camp, Darling said his campaign's polling returns showed beyond doubt that Scotland would vote to reject breaking up the 300-year-old union.

"We will win and I know that because I can see our returns," Darling, the head of Better Together, told journalists. "We will win, be in no doubt about it. I know, because I see them every day, our returns are good."

Better Together said it had the support of more than 50% of voters who had made up their minds, but would keep campaigning down to the wire.

An Opinium poll for this paper puts the no campaign on 53% against 47% for yes, among those certain to vote and excluding "don't knows". Fewer than 3% of those on each side say there is any real chance of them changing their mind.

It would appear that the yes campaign now needs to win over all the "don't knows" and change some minds among fixed no supporters if Alex Salmond is to declare his dream of independence a reality early on Friday morning.

In an exclusive interview with the Observer, Salmond struck an upbeat note, saying he could still win over enough no voters. "All those who intend to vote no right now are simply deferred yeses," he said. "Referendums are very special occasions because every single vote counts. There are no such things as safe seats or marginal ones; none that take priority over others."

Salmond attacked the narrow focus of the no campaign: "Their people have decided there are certain special categories that they can target, such as the rich, the powerful and the landed aristocracy. I, though, want to go for every vote."

A week ago, the no campaign and all the main Westminster parties were shaken by a YouGov poll that showed a two-point lead for yes as the campaign entered its final leg. It prompted the Conservatives, Labour and Liberal Democrats to promise more powers for Scotland on an accelerated timetable, as they tried desperately to demonstrate that a no vote would not result in the status quo.

Writing in the Observer, Labour leader Ed Miliband promises that his party would lead a constitutional revolution "from Cornwall to Cumbria", including reform of the House of Lords. The Labour leader says that devolution plans spelt out last week were "just the start of the change we need in where power lies".

Miliband adds: "Scotland has led the way but devolution is not a project just for Scotland. Further devolution is coming to Wales. And Scotland's example will lead the way in changing the way we are governed in England too."

The former prime minister Tony Blair, who has been absent from the debate, said he hoped the vote would go against independence.

"I hope Scotland votes to stay part of the UK," Blair, who was born in Scotland, said at a security conference in the Ukrainian capital, Kiev. "For all the reasons given by all the party leaders of the UK, in the 21st century to rip up the alliance between our countries would not be sensible, politically, economically or even emotionally."

Miliband's message has been echoed by Tory, Labour and Lib Dem leaders in local government who, in a joint letter to the Observer, say that promises of devolution to Scotland must be matched by immediate transfers of power to local authorities in England, if the English are not to end up feeling like "second-class citizens".

Putting aside political differences, the three leaders of the Local Government Association's political groups say: "Our local areas need the same freedoms to tackle the big issues for residents, from schools and jobs to welfare and housing.

"Establishing an English parliament would not represent true devolution. Instead we need locally elected councils driving local economies through devolved taxation, with greater control over council tax and business rates.

"We need local areas freed from government-imposed restrictions on housebuilding. And we need funding for regeneration, skills and jobs devolved to local areas where decisions can be based on what businesses and young people actually need. Crucially, this must be underpinned by a fairer funding system for all of the UK.

"We urge government to set out a timetable for devolution across England, with a pledge for immediate new powers for areas ready for them now."

On Saturday, leading telecoms companies, including BT and Vodafone, joined those firms warning that independence would have negative consequences, saying they could face increased costs if Scotland voted yes. In a joint statement, six telecoms company chief executives said they might need to "modify the services offered in Scotland, given its relatively demanding topography and relatively low population density. Any of these factors could lead to increased industry costs."

On Saturday, Salmond fuelled an acrimonious row over the alleged leaking of Royal Bank of Scotland's intention to relocate to England from an independent Scotland by claiming that he had uncovered evidence of foul play by the Treasury.

Brandishing an email sent by the Treasury to journalists, which appeared to suggest officials had passed on RBS's plans before the bank had even finished a Wednesday night board meeting discussing the issue, Salmond said: "This is extraordinary. The Treasury have been caught bang to rights leaking market sensitive information while a Royal Bank board meeting was in session which took the decision which the Treasury had already leaked."

In a separate clash, shadow business secretary Chuka Umunna, described comments by leading yes campaigner Jim Sillars in which he warned of a "day of reckoning" for anti-independence businesses as "a complete disgrace". Umunna added: "Seek to win by the strength of your argument, not through ugly rhetoric."

Nearly 4.3 million people have registered to vote on Thursday – 97% of those eligible. While it is unlikely that all of those registered will vote, the referendum is set to be the biggest poll in Scotland's history with an expected turnout of well over 80%.

David Cameron will return to Scotland on Monday to make what aides described as a "highly personal" speech in favour of the union, in which he will reiterate his view that Scottish people can have the "best of both worlds" inside the union with more devolved power.