A former SNP MSP has become the latest member of the Scottish Green Party, its Scottish leader Patrick Harvie announced.

Highlands and Islands MSP John Finnie revealed he was joining the party as it met for what is its largest ever conference.

Since the independence referendum less than a month ago, the Scottish Green Party has more than trebled its membership, with some 6,300 people now in the party.

Mr Finnie told the party's conference in Edinburgh: “The language of the Green Party is the language of social justice and environmental justice and I am proud to be associated with it.”

The former police officer has been a member of the Scottish Parliament since May 2011, when he was elected as an SNP MSP for the Highlands and Islands region.

But he resigned from the party in 2012, after it reversed its policy stance on Nato membership so that an independent Scotland would seek to become part of the international organisation.

Since then Mr Finnie has remained in Holyrood as an independent MSP, and is part of a group of Green and independent MSPs there.

While he has joined the Scottish Green Party he will continue to sit as an independent MSP until the next Scottish elections in 2016, when he will seek to stand as a Green Party candidate.

He was given a standing ovation at conference after Mr Harvie, the Scottish Green co-convener, announced: “I am delighted and excited to be able to tell you that the most recent new recruit to the Scottish Green Party is John Finnie MSP.”

He added: “The Scottish Greens have seen an unprecedented surge in membership over the last month. To be able to tell conference that John is the latest of those new members is therefore an extraordinary privilege.

“John's decision to join the Scottish Greens comes at an excellent time. As a country, as a Parliament, and as a party, we face significant challenges on austerity and inequality, on further devolution, and on building a just low-carbon economy. Working alongside him we will aim to make a real difference on all those issues, to hold both governments to account, and to campaign for an stronger Green group at Holyrood after May 2016.”

Mr Finnie said: “I would like to thank the Scottish Greens for my welcome to the party today, which has been warm, generous, and enthusiastic.

“I've been a Green all my life; I just didn't know it. Working and campaigning alongside Greens, I've seen that my values are Green values, social and environmental justice, democracy and integrity, internationalism and peace. Receiving my membership card today feels like a homecoming.

“I have no ill will towards the SNP, a substantial minority of whom voted with me to oppose Nato membership. But the project of building a fairer and more sustainable Scotland isn't the exclusive property of one party, or even any group of parties, and I would urge others who share my views to take the next step and join the Greens as I have done.

“I'll continue to sit as an independent MSP for the rest of this parliament, voting for the manifesto commitments I stood on, and voting with my conscience and judgment in all other votes, as I have done since becoming an independent. I'll be putting my name forward to be selected as a Green candidate for the Highlands and Islands for 2016, a decision which will be for the local branch to make.”