Scotland's First Minister Humza Yousaf announces his resignation during a statement, at Bute House, in Edinburgh, on Monday. AFP

Scotland's leader Humza Yousaf resigned on Monday, further opening the door to the UK opposition Labour Party to regain ground in its former Scottish heartlands in a national election expected later this year.

Yousaf quit as head of the pro-independence Scottish National Party (SNP) after a week of chaos triggered by his scrapping of a coalition agreement with Scotland's Greens.

He then failed to secure enough support to survive votes of no confidence against him expected later this week.

Resigning little over a year after he replaced Nicola Sturgeon as first minister and SNP leader, Yousaf said it was time for someone else to lead Scotland's devolved government.

The SNP's fortunes have faltered over a funding scandal and the resignation of Sturgeon as party leader last year. There has also been infighting over how progressive its pitch should be as it seeks to woo back voters.

Caught between defending the progressive record of the coalition government and some nationalists' demands to jettison gender recognition reforms and refocus on the economy, Yousaf was unable to strike a balance that would ensure his survival.

The SNP is losing popular support after 17 years of heading the Scottish government. Earlier this month, polling firm YouGov said the Labour Party had overtaken the SNP in voting intentions for a Westminster election for the first time in a decade.

Labour's resurgence in Scotland adds to the challenge facing British Prime Minister Rishi Sunak's Conservative Party which is lagging far behind Labour in UK-wide opinion polls.

The Scottish parliament now has 28 days to choose a new first minister before an election is forced, with former SNP leader John Swinney and Yousaf's former leadership rival Kate Forbes seen as possible successors.

If the SNP is unable to find a new leader to command support in parliament, a Scottish election will be held.

Reuters