The development came in the wake of a TNS BMRB poll for The Herald, which showed on a straightforward yes/no question that 50% of people were opposed to Scottish independence and 30% were in favour.
This is a record 20-point lead for the anti-independence camp and was generally regarded as a boost to the Better Together campaign.
On a second question asked by pollsters, which included the "more powers" option, support for independence fell three points to 23% during the past six months and support for the Union fell by three points to 29%. However, support for more powers rose by seven points to 37%.
Alex Salmond and his colleagues thus far have made clear their personal preference is for a single yes/no question on independence but have stressed their open-mindedness towards the devo-max option.
It is thought the First Minister will make his and the SNP Government's position clear when the results of Holyrood's consultation on the referendum are published in the autumn.
Yet yesterday, on the back of the latest poll figures, Angus Robertson, the Nationalist campaign director, talked up the "more powers" option.
He added the pro-independence figure to the pro devo-max figure to argue that 60% of Scots rejected the status quo and favoured "progress for Scotland".
Mr Robertson said: "This poll puts further pressure on the anti-independence parties who are offering nothing to Scotland.
"It follows calls from Labour's biggest trade union backers Unite for a 'more powers' option, which is also backed by much of civic Scotland as well as Tory donor John McGlynn and leading businessmen Sir Tom Farmer and Jim McColl."
He added: "This simply reinforces the case that the referendum must be made in Scotland without any Westminster strings attached."
Opponents of independence were buoyed by the poll, saying it showed the momentum was clearly with the pro-UK forces, particularly as Patrick Harvie, co-convener of the Scottish Greens, signalled his party, having backed a multi-option referendum, was now likely to support a single yes/no question on the ballot paper.
Mr Harvie said: "To be legitimate, a second question needs to be clear and it needs to represent a meaningful mandate."
He added: "A couple of organisations have tried to define what devo-max or devo-plus might look like. I don't think they have achieved the clarity that's needed for people to know what they are voting for."
Last night, Ruth Davidson, the Scottish Conservative leader, described Mr Salmond as the "last man standing in his backing for a second question".
She explained: "First he was abandoned by Margo MacDonald and now the Greens have seen how confusing it would be to have a multi-choice referendum.
"Even those in charge of running Alex Salmond's separatist campaign have said it would make sense to offer people a single, straightforward question on whether Scotland should leave the United Kingdom.
"With the polls showing another drop in the number of Scots backing separation, no wonder Alex Salmond is scared stiff of a simple question on separation," she added.
Labour's Patricia Ferguson described the latest survey as a "great poll for Scotland and for the majority of Scots who want to stay part of the UK".
She said that, faced with rejection, the First Minister was now "desperate to find a way out of this dilemma but the growing support for a single question – across parties and across Scotland – is fast becoming overwhelming".
Jo Swinson, deputy leader of the Scottish Liberal Democrats, claimed the Nationalist-led campaign was now "completely detached" from most Scots.
"When a third option is added to the choices available, independence drops to the third most popular option," she noted, adding: "Most people wish to see a stronger Scottish parliament within a United Kingdom."
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