Nicola Sturgeon’s legacy was delivered a parting blow as it emerged the party has lost 42% of its members in three years.

Figures produced by the party following demands from the leadership candidates show membership has plunged from 125,000 in 2019 to 72,000.

An internal email by Lorna Finn, the SNP’s national secretary, shows that there were 82,600 members in December, indicating a sharp fall as the government was embroiled in the gender reform bill, strikes and further debate over the unfinished ferries.

Kate Forbes’s campaign team said that “the alarming drop in members shows that the party needs a change in direction”.

The finance secretary had written a joint letter to the party with rival candidate Ash Regan demanding the figures were published. Humza Yousaf, the health secretary, also called for transparency.

Ms Forbes and Ms Regan want independent auditors to oversee the vote and have also called for Peter Murrell, Ms Sturgeon’s husband, to release key information about his role as the party’s chief executive.

Ms Regan said the membership drop coincided with the passing of controversial gender reforms that allow for self-identification and lower the age at which people can change their gender to 16.

She said the fall in membership hastened Ms Sturgeon’s decision to quit. “We’ve lost some good people and I want to see us build our membership numbers and attract people back to the party,” she said.

Ms Yousaf welcomed the publication of the figures yesterday and attacked his opponents for questioning the SNP headquarters operation.

“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,” he said.

Confirmation that the membership had fallen was embarrassing for the party’s press office which had described the figures published by the Sunday Mail as being “not just flat wrong, it’s wrong by about 30,000”. The party has been regularly and wrongly reporting that membership was still about 100,000.

After the figures were published Alex Salmond, the former first minister and a stern critic of Sturgeon, tweeted: “It takes decades to build a political party but days to destroy one.”

An SNP spokeswoman blamed the cost of living crisis. She 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.”

Amid internal concerns that the party will struggle to unite under whoever is chosen to be the next leader, Ms Sturgeon told reporters after First Minister’s questions: “Growing pains for any organisation can be painful but they are important and the party is going through a process.

“As I said last week, I think it is incumbent on the three candidates that are standing to succeed me that they remember that the task is to retain the trust of the Scottish people that we have won consistently over not just the eight years of my leadership but consistently since 2007.”