PATRICK Harvie has cautioned against holding an early re-run of 2014's independence referendum.

The co-convener of the Scottish Greens - who are hoping to win regional votes from SNP supporters in the Holyrood election - warned against letting June's EU referendum become a trigger for a second independence poll.

In an interview with The Herald, he said it would be harder to make a case for independence if Britain was outside the European Union.

He also warned a future Yes campaign would need a "much stronger proposition" than two years ago, when he said the SNP's currency plan "did not stack up".

The Scottish Greens, who had two MSPs in the last parliament, are hoping to win a record 10 seats on May 5.

The pro-independence party is targeting SNP supporters who back Nicola Sturgeon but want her government to be more radical on tax and environmental issues.

Read More: Greens back tax hikes on rich and attack SNP for "startling lack of ambition"

The Greens experienced a huge surge in membership after the independence referendum, and will fight the Holyrood campaign with around 9000 activists, ten times the number they had before the 2011 poll.

But despite their referendum boost, Mr Harvie was wary of rushing into a second independence battle.

Asked whether Brexit should trigger a second independence referendum, if a majority of Scots voted to stay in the EU, he said: "It will certainly prompt a lot of people to demand one.

"They might well be justified.

"Being justified isn't enough, though, because we would need to be very clear about what happens in the event of Scotland voting for independence in the event of a Brexit.

"One of the questions that was not satisfactorily answered during the independence referendum was what would be our terms and conditions of EU membership.

"Would we inherit the UK's terms and conditions or have to negotiate from scratch?

"If the UK is walking out of the door, that becomes a tougher question to answer."

He added: "The priority for those who support Scottish independence and support membership of the EU has to be to win that vote for remaining in the EU as strongly as possible.

"I think that is by far the stronger context for the independence movement is a vote throughout these islands to remain in the EU."

Last year a Brussels-based think tank, Friends of Europe, highlighted a number of potential difficulties for a future Yes campaign if Britain left the EU.

They included the prospect of creating a "hard border" between an independent Scotland entering the EU as a member state and a UK outwith the bloc.

Nicola Sturgeon has said a second independence referendum would "almost certainly" be demanded if the UK were to leave the UK despite a majority of Scots voting to stay.

However, she has been careful to stress she will not call another referendum unless she was certain of victory.

Speaking earlier, during a Q&A with readers on The Herald's Facebook page, Mr Harvie said he was in "no doubt" a second referendum would take place at some stage and that he would again campaign for a Yes vote, though for different reasons from the SNP.

He said independence offered the only way to "transition away" from a fossil fuel economy and to end austerity.

He added: "There were areas like currency where the SNP's proposition in 2014 just did not stack up.

"It did not convince enough people.

"So we need a much stronger proposition if we are not just going to have another referendum for the sake of it but actually convince a clear majority of Scotland that this is right, that this is a good thing for Scotland and for our neighbours as well."

Mr Harvie also pledged to publish his tax returns and said all Green MSPs would do so in future, in the wake of the Panama Papers scandal.

He said: "People who make tax policy for other people - and that's what the Scottish Parliament will be doing from now on - should be transparent about these things."