Former Scottish Green MSP Robin Harper has quit the party, criticising his former colleagues over their support of transgender rights and independence. 

The former modern studies teacher, who represented Lothian between 1999 and 2011, said he would now be voting Labour.

He claimed Patrick Harvie and Lorna Slater had "forgotten about the centre of Scottish politics."

A spokesman for the Scottish Greens said the party — now in government — was “delivering what Robin and others could only have wished for back in the early days of devolution."

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In a letter to the party’s co-convenor, Patrick Harvie, obtained by the Times, Mr Harper said he had misgivings about certain issues going back 20 years. 

“As you know, I am politically left of centre, and with the [Scottish Socialist Party] to the left of us I felt the SGP was in the right place.

“I have watched with some concern the Scottish Green Party moving into the gap left by the Socialists in content, and also adopting their stridency of expression.”

He added: “You will also be aware of my serious concerns about the way we are handling the situation with the trans community.

“There may be little point in my expressing my views at this stage, but hopefully the Scottish parliament will return to listening mode when the Cass and Sandyford reports have been published.

“I believe that a complete overhaul of the way our child and adolescent mental health services are working is essential and urgent.”

Mr Harper's letter continued: "My concern that the SGP's public image has been damaged by its failure to co-operate meaningfully with other interests, including the Westminster government, is reinforced by the huge number of friends, acquaintances and random contacts who have expressed to me an opinion that the Scottish Green Party has lost the plot.

"I am aware that former colleagues and friends in the SGP may be sorry - and even offended - by my decision to resign from the party and I apologise for not attempting to speak up within the party before coming to this decision."

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On the BBC's Good Morning Scotland, it was put to Mr Harper that the party was electorally successful in a way that it had not been during his time in Holyrood. 

"They are chiming with part of the electorate," he said. "I would far rather that they try with more than part of the electorate. The centre of politics in any country is an important place to be for at least part of your agenda.

"I am really quite concerned that the Green Party, as it is at the moment, the present leadership, have forgotten about the centre of Scottish politics."

He was also asked about the Deposit Return Scheme. Earlier this year, the Scottish Government delayed the launch by another two and a half years.

Circular Economy Minister, and Green party MSP, Lorna Slater blamed the UK Government, after ministers in Whitehall made clear the Scottish Government would only be given the necessary exemption to the UK Internal Market Act if they made a number of substantial changes.

This included removing glass from the scope of the scheme and a demand that ministers in Edinburgh agree to standardise the deposit charge and labelling with the other UK schemes.

Ms Slater said the lack of detail around conditions laid down by Whitehall, including not knowing what the deposit charge would need to be, meant the scheme could not go ahead as planned.

However, that was disputed by the UK Government, who said the delay entirely a decision made by the Scottish Government, and that their call to exclude glass was made after the drinks industry industry concerns.

Mr Harper said this was a "totally needless bust up."

"And the cooperation was there on offer from Westminster," he added. "It wasn't refused. But by the time we had passed the legislation and set up everything to do it the way that Lorna Slater wanted to do it. It was too late."

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A spokesperson for the Scottish Greens said: "We thank Robin for what he has done both within parliament as the first ever Scottish Green MSP and outside it as a tireless advocate for the environment.

"Our party has always been committed to social and environmental justice as well as to independence.

"With Scottish Greens now in government, we are turning long-held policies such as free bus travel for young people, investing in restoring Scotland's natural environment, and a cap on rent rises into reality.

"This is delivering what Robin and others could only have wished for back in the early days of devolution."

The Herald:

The spokesperson added: "Independence and human rights, including the rights of trans people, are at the core of our vision and have been since our party was founded over 30 years ago.

"Our commitment to that vision has seen us achieve record result after record result in recent elections.

"The climate crisis will be the defining environmental issue for this generation and all future generations. It is only by building on this green change that we can deliver a fairer, greener and better future for Scotland."

Scottish Conservative chairman Craig Hoy said: "The SNP First Minister should not continue to be in thrall to the extremist and anti-growth Greens, who he is using to help push his independence obsession rather than focusing on Scotland's real priorities," he said.