The Scottish independence campaign will be launched in May more than two years before the yes campaign's preferred date, First Minister Alex Salmond said.

Mr Salmond, who won an unprecedented majority in the Scottish Parliament last year, said it would not be run only by the SNP but would feature a "broad-based" range of supporters, including unions and employers.

In an interview with the BBC's Sunday Politics programme, Mr Salmond said he wanted a long campaign, with the referendum in autumn 2014, to ensure voters in Scotland had answers to all the open questions about the implications of the decision.

He said opponents of independence seemed to agree on nothing but the need to say no and pledged his party would be able to answer all voters' questions.

Mr Salmond said: "The people who seem to argue for a no seem to be in no fit position to argue their case. They don't even know what their case is.

"I think it is important when we come to the referendum in 2014 people will have an exact proposition on independence, which I pledge to give. All of the questions (will be) answered to people's satisfaction.

"I think we will win the referendum. In fact, so confident are we about winning the referendum, shortly after the local elections in Scotland in May and when the final position on the Scottish Government's consultation, which is I think May 11, then the yes campaign will be launched.

"That won't just be the Scottish National Party. That will be a broad-based campaign with civic Scotland, job creators of Scotland, with the unions of Scotland, a variety of people coming together to enunciate the case for Scotland. There will be a positive approach which will contrast very markedly with the opponents united only in their negativity."

Mr Salmond was pressed during the interview on the economics of such a move and what keeping the pound would mean for a newly independent Scotland.

He said the SNP would be promoting a new "sterling area" which would involved a fiscal stability pact, meaning limits on borrowing.