Joanna Cherry resigned from the SNP's ruling committee.
Cherry accused the party's leadership of being secretive, evasive, and menacing.
She criticized the lack of transparency around the party's finances.
Cherry cited inability to improve transparency and scrutiny as the reason for her resignation.
The SNP has been under police investigation for its financial affairs.
Former chief executive Peter Murrell was arrested and released without charge.
Cherry had long-standing concerns about transparency within the party.
She cited inadequate business conduct and a menacing atmosphere in the National Executive Committee (NEC).
Cherry's resignation followed the departure of Douglas Chapman as party treasurer.
The SNP's accountants also quit amid the fraud investigation, adding to the party's turmoil.