The Scottish Green Party will vote against Scotland's Humza Yousaf in a vote of no confidence in him as first minister, a source within the party said on Thursday.

Yousaf's other opponents said earlier on Thursday they would seek to oust him as Scotland's leader after his Scottish National Party abandoned a coalition with the Greens.

Yousaf, who serves as first minister in Scotland's devolved government, ended the alliance on Thursday. The arrangement had come under strain after a decision to scrap a climate change emissions reduction target last week.

The SNP has led Scotland's devolved government since 2011, but its fortunes faltered since a funding scandal and the resignation of a party leader last year.

The party holds broadly centre-left views, but its coalition with the Greens had highlighted splits over how progressive its pitch should be as it seeks to woo back voters on social and environmental issues beyond its core call for independence.

Earlier this month, a YouGov poll put the main British opposition Labour Party slightly ahead of the SNP in Scotland for the first time since Scottish voters chose to remain part of the United Kingdom in an independence referendum in 2014. (Reuters)