Ash Regan is among seven SNP MSPs who felt unable to support the plans as they faced their first Holyrood vote.
An SNP minister has resigned over Scottish government plans to make it easier for someone to change their legally-recognised gender.
Ash Regan quit as community safety minister, saying her conscience would not allow her to vote with the government.
Her resignation came ahead of the proposed changes to the Gender Recognition Act facing its first vote at Holyrood.
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