“I love ambition, but it only matters if you actually deliver against that,” he said.
“Now what we’ve seen in this week is desperately disappointing from the Scots, they’ve pulled away essentially the target framework, almost in its entirety, leaving the net zero target, but removing the targets for 2030 and 2040.
“And the reason they’ve done that is because the 2030 target was over-ambitious.”
Humza Yousaf has also come under pressure from within his own party to end the power-sharing deal.
Kate Forbes, whom Mr Yousaf only narrowly defeated in the SNP leadership contest just over a year ago, is among those who have called for the Bute House agreement to go.
In December she said, external “nearly all the issues that have lost us support in the last year are found in the Bute House agreement and not in the SNP manifesto.”
The Greens, said Ms Forbes, had a progressive, ideological agenda which was unpopular in the country at large and were also hitting rural communities with over-regulation and tax hikes.
The party has been involved in several difficult policy issues, with legislation stalling on issues including protecting the oceans and recycling bottles.