The SNP must understand why 30,000 members left the party in just over a year, two of the contenders to succeed Nicola Sturgeon have said.

Membership figures released following pressure from all three candidates in the race showed the drop between the last published figures and the beginning of the leadership contest.

A row ensued over the numbers, leading to the resignation of chief executive Peter Murrell and head of communications Murray Foote over incorrect comments made to journalists who asked about membership last month.

Speaking during a debate on Monday on LBC Radio, Humza Yousaf said it would be for a new leader to find out why so many have left the party.

“First of all, the new leader, one of the first things they have to do internally is get in amongst the weeds and understand why we lost those members,” he said.

“Is it because, for example, people don’t view we’ve made enough progress on independence and been talking too much about process and not enough about policy?”

Asked the same question, former community safety minister Ash Regan said: “I’ve been obviously talking about this over the last few weeks, and I was the first to say, as part of this hustings that I suspected that we had lost a large number of members over the last wee while.

“Obviously it’s anecdotal – I don’t have the data on this – I imagined the party perhaps does keep data on the reasons that people give when they relinquish their membership, but my assessment of it was it was just down to a lack of perceived progress on the independence question, and also the gender recognition reform.”

She added: “When large numbers like that leave, I think the sensible thing to do is to look into that and say, ‘why are we losing members and what can we or should we be doing about it?’

“I’m the only candidate here that set out an SNP action plan when I first announced my candidacy several weeks ago, the idea behind that being that we need to make members feel valued, we need to reflect the interests that they have, we need to modernise the party and bring back the democracy that I think is missing.”

Ms Regan went on to say some people had written to her since she announced her candidacy to say they would re-join if she became first minister, adding that “they consider me to be the only hope for the party at this juncture”.