Two-thirds of Scottish Green members backed an agreement which could see the party join the Scottish Government alongside the SNP. Party members voted to support the deal to enter government at an extraordinary general meeting (EGM) this morning following a two-hour debate and subsequent ratification by the Green council.
715 members (88.5 percent) backed the deal while 84 (10.4 percent) voted against and nine (1.1 percent) abstained.
At the heart of the pact is a commitment to a second independence referendum within five years, and preferably by the end of 2023.
Although Boris Johnson would still have to grant permission for a legal vote, the Scottish Government now has a built-in majority for its referendum bill.
The SNP Cabinet approved the informal power-sharing deal with the hard-left pro-independence minority party last weekend.
The two parties have been locked in talks since May, when the SNP fell one seat short of an overall majority at the Holyrood election.
Under the powersharing deal, Mr Harvie and fellow co-leader Lorna Slater would become government ministers with one responsible for green skills, the energy industry and the natural environment.
Meanwhile, the second will be responsible for decarbonising homes and transport and the rental sector.
Scottish Green MSPs will also be required to back the Scottish Government in confidence votes and annual budgets as they work on a raft of agreed policy areas, including tackling the climate emergency, Scottish independence and rent controls.
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Public disagreement between the parties would only be allowed on a set of agreed topics, such as aviation policy, green ports, direct financial support to businesses involved in the aerospace, defence and security sectors, field sports and the economic principles related to concepts of sustainable growth and inclusive growth.
But Scottish Labour leader Anas Sarwar said the agreement would "make it harder" for parliament to hold the Scottish First Minister "to account".
Mr Sarwar added: "This coalition of cuts is formalising a long-standing agreement where Nicola Sturgeon and the SNP hammer our public services and the Greens nod along.
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“The SNP is desperate to avoid scrutiny and this coalition with their Green branch office is simply designed to make it harder for parliament to hold the First Minister to account."
Nicola Sturgeon said both parties would "work collaboratively" to support a "fair recovery from Covid, address with urgency the impacts of the climate emergency, and give the people of Scotland a vote on independence".
She added: "The agreement recognises that co-operation and consensus are essential to finding the practical solutions to the big challenges we face, and it echoes the founding principles of our Parliament.
“While our parties do not agree on everything, we have much common ground. We also have a determination - and indeed a responsibility - to look beyond our differences to build a better country."
Patrick Harvie MSP, Scottish Greens co-leader, said: "I am delighted that our party members have given their support to this historic cooperation agreement that will see Greens enter government for the first time in Scotland, or indeed anywhere in the UK.
"With Greens in government we will be able to deliver positive change for the people of Scotland.”