SNP leader Nicola Sturgeon today left the door open to a second referendum on Scottish independence before 2020 . Before last year 's historic vote , Scottish nationalists insisted it was a once-in-a-generation chance to decided on the future of the 300-year-old Union . But Ms Sturgeon today refused to rule out demanding a re-run within the next five years , prompting opponents to claim she had 'broken a promise the size of Ben Nevis ' . SNP leader Nicola Sturgeon today refused to rule out demanding a re-run within the next five years , prompting opponents to claim she had 'broken a promise the size of Ben Nevis ' In September 's vote , 55 per cent of Scots backed the idea of remaining in the United Kingdom . Alex Salmond said the vote was an 'opportunity of a lifetime ' and two years ago , Miss Sturgeon said of the independence vote : 'We have always said it 's a once in a generation thing . ' But in a series of TV election debates between Scottish leaders , Ms Sturgeon has shifted her position and today left open the possibility that the promise of another vote could be included in a future SNP manifesto . Under pressure she said that 'something would have to change ' before she promised a referendum , and people would have to vote for it . She said : ' I am not planning another referendum right now , there is not another referendum on the cards . 'In order for another referendum to be in an SNP manifesto in future , something significant would have to change from the situation we had last year in the referendum . ' Ms Sturgeon , who was campaigning in Paisley today , left open the idea of demanding a referendum in next year 's Scottish Parliament elections . Opponents claim Ms Sturgeon had 'broken a promise the size of Ben Nevis ' on a referendum , after insisting last year 's vote was a once in a generation event . During a fractious and at times shouty debate on BBC Sunday Politics Scotland , Scottish Tory leader Ruth Davidson challenged her to rule out another vote . Ms Davidson , leader of the Scottish Conservatives , added : 'You clearly do n't want to tell people before they vote in this election , what will happen in the next election . 'You have a conference coming up in September , you have 80,000 new members who might be popping along , are you going to put a motion at your conference on this to put a referendum into your next manifesto ? ' Ms Sturgeon said : ' I am not planning another referendum right now , I have n't published the 2016 manifesto . It will be this time next year before we publish the 2016 one . ' Mr Rennie said the SNP leader had 'broken a promise the size of Ben Nevis ' on another referendum . He said : 'People need to know whether their vote for the SNP this time round will trigger a referendum in the SNP 's manifesto in 2016 . Nicola Sturgeon 's refusal to answer this basic question makes clear that Scotland faces neverendum . 'It matters because during the referendum we know the SNP took their eye off the ball . As a result , public services were neglected . 'We have seen from Canada the economic impact of an uncertain constitutional environment . Quebec lost jobs and wealth . That damaged the province in the long term . I want a Scotland which builds a stronger economy and a fairer society , balancing the books and delivering more powers . ' During a TV debate , Scottish Labour leader Jim Murphy and Tory leader Ruth Davidson challenged Ms Sturgeon to come clean on her plans for Scotland . Ms Sturgeon later accused her opponents of 'reviving Project Fear ' . The First Minister was questioned about SNP plans to increase Scotland 's financial powers , which economists have suggested would leave a £7.6 billion spending gap , during a third televised election debate in under a week . Ms Sturgeon said that full fiscal autonomy would take several years to implement but with new powers Scotland would start growing its economy and revenues . She said : 'This week we 've seen the Project Fear that dominated the referendum revived by these three unionist parties , trying to talk down Scotland and assert that we 're not capable of running our own affairs . ' Scottish Conservatives leader Ruth Davidson said : 'This ( the figure ) did n't come from us . You 're right in saying this came from the Institute for Fiscal Studies . It also came from a group of Scottish-based economists that projected the gap to be bigger . ' Scottish Labour leader Jim Murphy said : 'To make this £7.6 billion up Scotland would have to grow at twice the rate of the rest of entire advanced world , so how would you do that Nicola ? '
SNP leader refuses to rule out calling for another vote on independence . Scottish had called last year's referendum 'once in a generation ' Opponents accuse Sturgeon of breaking a 'promise the size of Ben Nevis '