THE Scottish Greens will pledge to make a future SNP government "bolder and greener" in a copycat campaign that could deny Nicola Sturgeon a Holyrood majority but also decimate Labour.

Patrick Harvie's party believes it can return a dozen MSPs at the Holyrood election now less than a year away.

Party insiders say they will model their strategy on the SNP's successful UK election campaign, when Ms Sturgeon talked up the prospect of a minority Labour government made "bolder and better" by an alliance with the Nationalists.

They believe the message will appeal to disillusioned former Labour supporters, who might still be wary of the SNP gaining a second successive majority.

But they also believe diehard SNP supporters will be willing to lend their regional vote to another pro-independence party if it reduces Labour's chances of winning regional seats.

A senior source said: "If you are an SNP voter in your constituency, what do you do with your list vote?

"If you give it to the Greens, our numbers go through the roof and Labour's go through the floor."

The source added: "We are almost in a siutuation where SNP voters, with two votes next year, could choose the party of government and the main party of opposition."

As in previous elections, the Greens will focus their effort on trying to win regional seats, which are elected by a proportional voting system and account for 56 of the 129 Holyrood total.

Current MSPs Patrick Harvie and Alison Johnstone top the party's Glasgow and Lothian lists respectively.

Two other well-known names, Maggie Chapman, the party's co-convener, and John Finnie, who defected from the SNP, are in prime spots in the North East region and Highlands and Islands.

The party also is hopeful Andy Wightman, the land reform campaigner, will become an MSP from his position in second place on its Lothians slate.

In the Edinburgh area, the Greens believe they can pick up a substantial slice of the votes that went to the late Margo MacDonald, the Independent MSP, in previous elections.

The source said: "Here is a chance for people have someone to the left of the SNP.

"People wanted lots of Nats to make the Labour Party better. That's where we are with the SNP.

"We'll send a message to everyone on the left: we are the party to keep the SNP progressive.

"People are losing faith with Labour by the day.

"We need someone to hold the SNP to account and push them in the right direction."

During the General Election Ms Sturgeon suggested voters in England should vote Green.

She saw the party as part of a potential "progressive alliance" at Westminster before the Conservatives emerged with a small overall majority.

The SNP leader appeared to forge a good relationship with Greens leader Natalie Bennett, sealed in a famous "group hug" together with Plaid's Leanne Wood at the end of a televised debate.

Polls suggest support for the party is running at between 8 per cent and 10 per cent, with one recent survey giving them a 13 per cent share.

Membership has soared from 1700 to 9000 since the referendum, when the Greens were part of the official Yes Scotland campaign, giving the party a much stronger activist base going into next May's poll.

One in 10 of the new members is ex-Labour, the party says.

Party insiders say the have learned from campaigning on a bigger scale for the first time during the General Election.

"We are gearing up, our candidates are ready and our party branches have cut their teeth in the election just gone.

"Our polling is good, it is there for us to do."

The Scottish Greens claimed a 1.3 per cent share of the vote on May , up 0.7 per cent on the 2010 election.

Across the country 39,205 people backed Mr Harvie's party.

At the last Holyrood election in 2011, the party achieved a 4.4 per cent share of the regional vote, a slight improvement on 2007, and enough to preserve its tally of two MSPs.

Just over 87,000 voters backed the Greens, who campaigned for a huge extra investment in energy efficiency measures, to scrap the new Forth crossing and to replace council tax with a land tax.

In the same election, the Scottish Conservatives picked up a dozen regional seats with a 12.4 per cent share of the list vote.

The Greens' best showing was in the 'rainbow parliament' of 2003 to 2007, when they returned seven MSPs after capturing 7 per cent of the list vote.

More than 132,000 Scots gave the party their second vote in the 2003 election.