She had unsuccesfully challenged former MP Kenny MacAskill for Alba’s leadership earlier this year.
The Alba Party’s sole MSP Ash Regan has left the party to sit in Holyrood as an independent.
The Edinburgh Eastern MSP was elected under an SNP banner, though later quit and gave up a ministerial position to protest against gender recognition reforms.
In October 2023 she joined the pro-independence party founded by Alex Salmond and unsuccessfully challenged former MP Kenny MacAskill for Alba’s leadership earlier this year.
A rift within Alba has been clear for some months, particularly around the closely fought leadership election.
When Mr MacAskill was announced as the party leader at an event in March, Ms Regan left the hall without giving any concession speech.
On Friday, LBC reported that the Edinburgh Eastern MSP had written to party members saying Alba had “chosen a different path” around her Unbuyable Bill – which aims to criminalise those who purchase sex.
She released a statement on Friday saying: “Today I have formally resigned from the Alba Party.
“My priorities and principles remain exactly as they were when I entered politics – to advance independence, protect women and children, and deliver competent government for Scotland.
“With my Unbuyable Bill entering a crucial stage, it’s clear that I can best focus on those goals as an independent MSP.
“I am grateful to the many Alba members and campaigners who have supported me, particularly the women who have stood with me for years.
“Public office is a privilege, not a possession.
“My full focus now is on building cross-party support to pass Unbuyable into law before the end of this parliamentary session.”
Former first minister Mr Salmond founded the party after leaving the SNP.
His death at a conference in North Macedonia in October last year left it searching for a new leader, with Mr MacAskill emerging as the winner.
