The SNP have lost around 30,000 party members since 2021.
The SNP reported a membership of 125,534 in December 2018. According to data published by the Electoral Commission, that dropped to around 104,000 by the end of December 2021.
On Thursday, the SNP admitted just 72,186 members were eligible to vote in the party leadership contest.
The number does not include those who joined the SNP after 15 February and are therefore not eligible for a ballot.
Commenting on the figures, the SNP said it remains “the biggest – and indeed the only mass membership – party in Scotland”.
However, SNP leadership hopeful Kate Forbes’ campaign team said that the drop in numbers “adds weight to the fact that it is time for a change”.
Michelle Thomson MSP added: “Whilst I’m pleased that common sense has prevailed with the publishing of the membership figures, the alarming drop in members shows that the party needs a change in direction.
“Kate Forbes is the candidate offering a new start for Scotland – continuity won’t cut it.”
Fellow candidate Ash Regan also issued a statement over the figures, simply saying: “I get things done.”
The figures have been revealed following widespread criticism of secrecy surrounding the SNP leadership contest.
Ash Regan, Ms Forbes and Humza Yousaf are currently in the running to replace Nicola Sturgeon as SNP leader and first minister.
On Wednesday, the trio piled pressure on their own party to be more transparent over the ballot process.
It came after concerns were raised over the exact size of the electorate after the Mail on Sunday reported that only 78,000 online forms were being sent out.
In an open letter to Peter Murrell, the SNP’s chief executive and Ms Sturgeon’s husband, both Ms Regan and Finance Secretary Ms Forbes called for the party to reveal the number of paid-up members, as well as the number of digital voting documents and postal voting papers issued.
Health Secretary Mr Yousaf also requested the information after candidates were reportedly advised that the number of votes, percentage share and turnout would only be published at the conclusion of the election.
Ms Forbes and Ms Regan also called for independent auditors to be brought in to offer assurances to SNP members and the public.
The requests came after candidates were reportedly advised that the number of votes, percentage share and turnout would only be published at the conclusion of the election.
Mr Yousaf welcomed the announcement of the figures, adding: “I trust this decision will also put to bed claims and hearsay that seek to undermine our party’s integrity and benefits only our opposition.
“As a party, we now need a progressive leader who can command support – ensuring our membership are engaged in the future of the party as we look to unite, and strengthen, support for the SNP and the wider independence movement.”
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The issuing of ballot papers and the counting and verification of votes is handled by independent company Mi-Voice. Mi-Voice has undertaken this function for the SNP since 2013.
The SNP said no one within HQ has access to live data from the ballot or any Mi-Voice systems, and no one will know the result until it is provided to the national secretary by Mi-Voice on 27 March.
The national secretary has written to the three candidates offering the opportunity to attend a meeting to “discuss the operation of the election rules”.
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Commenting on the membership numbers, an SNP spokesperson said: “After many years of delivering for people across Scotland and working towards a better future as an independent country, the SNP remains the biggest – and indeed the only mass membership – party in Scotland.
“We remain grateful to our large and committed membership for all their support which has done so much to fuel our electoral success.”