Politicians in pro-Union parties who are "privately enthusiastic" for Scottish independence should be allowed to speak their minds without fear of party discipline, Green leader Patrick Harvie has said.

The MSP said he met members of all parties who are "more open to independence than their parties will admit".

The comments were made as leaders held discussions on the staging of the 2014 referendum, at the invitation of First Minister Alex Salmond.

Labour, which did not comment on Mr Harvie's proposal, said after the meeting that there are still "many issues" to resolve.

Mr Harvie hopes the wider debate will not be split on party lines, allowing a free discussion on both sides.

Before the meeting he said: "Over the years I've met members of all parties who are more open to independence than their parties will admit, and it's not hard to find some who are privately enthusiastic. It's important for our democracy that they should feel free to speak their minds, and to campaign for a Yes vote without fear of party discipline.

"Independence has too often been seen as a simple split down party lines but the truth is more complex than that. Party leaders can sit down today and discuss the timing, the question, votes at 16 and a host of other issues. But the referendum is too important to be carved up between five people behind a closed door.

"Everyone in Scotland, including those in parties that don't support independence, must be free to campaign for the result they really believe in."

Scottish Labour leader Johann Lamont said: "There are still many issues to be resolved but I am glad that these talks are now under way and we have agreed to meet again next month to take this forward.

"This is Scotland's referendum and we must agree a process in which the Scottish people can have confidence."

Scottish Conservative leader Ruth Davidson said: "It is clear that more work needs to be done in order to get cross-party consensus on the issues surrounding the referendum.

"I welcome the opportunity for all party leaders to meet again next month.

"Scotland needs a fair, legal and decisive referendum in which we all can have confidence.

"Making that happen will allow us to move on to the more substantial debate around keeping Scotland in the United Kingdom."

Cabinet Secretary for Parliamentary Business and Government Strategy Bruce Crawford, who chaired the talks, said: "We had a useful discussion on a range of issues in the 'Your Scotland Your Referendum' consultation - including the Scottish
Government position that 16 and 17-year-olds on the electoral register should be entitled to vote in the referendum, as supported by NUS Scotland and Children First.

"These issues will continue to be discussed among the parties, but much more importantly across Scottish society - the key point is that the terms of the referendum must be decided in Scotland, and not dictated by Westminster."