The Scottish Parliament is "weaker" because of the Bute House Agreement, the former Scottish Green MSP Andy Wightman has said.
He is the latest senior figure to question the partnership deal between the SNP and his old party.
Last month, Robin Harper who served as a Lothians MSP between 1999 and 2011 and was co-convener of the Greens from 2004-2008, said the party had "lost the plot."
Mr Wightman, who quit the party in December 2020, following a row about the party's stance on transgender issues, told the Holyrood Sources podcast: "The only reason the Greens are in a coalition is because the SNP wanted it. And I never quite understood the rationale for that.
"I mean, Humza Yousaf defends it on the basis that they want a stable majority in Parliament and that's understandable, I suppose. But from a parliamentary point of view, you know, in the Parliament I was in, the executive did not have a majority."
Mr Wightman was a member of the cross-party committee set up to investigate how the Scottish Government bungled a probe into sexual misconduct allegations made against Alex Salmond in 2018.
The former first minister had the exercise set aside in a judicial review in January 2019, showing it had been “tainted by apparent bias.”
For months, the Scottish Government refused to hand over key legal advice to the committee.
It was only when the then deputy first minister John Swinney looked certain to lose a no confidence vote in parliament that they relented.
Mr Wightman told the podcast the minority government meant "that we could have meaningful votes of confidence in the Deputy First Minister, who was refusing until 6pm the day before to hand over critical evidence to the committee investigating harassment handling in the Scottish Government."
He added: "It meant that opposition parties can be doing work together to constructively come to amendments to various Scottish Government bills.
"And therefore parliament was stronger. So one of the consequences of this coalition is that parliament is weaker. And it's weaker because Humza Yousaf doesn't want it to be weaker."
A spokesperson for the Scottish Greens said: "Today of all days, as Westminster commits to a climate-wrecking oil field in Rosebank, it is clear why our positive green vision is so vital for people and planet."
Mr Wightman resigned from the party after an internal party argument over an amendment to the Forensic Medical Services (Victims of Sexual Offences) (Scotland) Bill regarding a sexual assault victim’s ability to choose who examines them.
It replaced the word “gender” with “sex.”
However, the Greens, including Mr Wightman all voted against.
In his resignation letter, he said he only did so due to a threat of “complaints and disciplinary action leading to possible suspension, deselection or expulsion”.
Mr Wightman added that he was previously censured by colleagues for attending of a public meeting at Edinburgh University in June 2019, which included gender-critical speakers.
“It has become evident to me that the sort of open-minded public engagement I would like to see take place on this topic is incompatible with a party that has become very censorious of any deviation from an agreed line.”