Senior Greens are examining ways to revamp the party’s structures to make it more effective and representative now its membership has more than tripled since Zack Polanski became leader.

Under the party’s direct-democracy model, policy is voted on only by members who attend one of its two annual conferences, a system some Greens believe risks empowering organised fringe activists who make the effort to travel to the events.

While no decisions have been made, one possibility would be for local parties to nominate delegates to speak and vote on behalf of members. Another option would be to keep one-member democracy, but allow online voting.

When Polanski became leader of the party in England and Wales last September, it had about 68,000 members. Now it has more than 230,000.

“There is a conversation in the sense that a lot of people are saying: the party has changed a lot, and the structures haven’t changed with it,” one Green official said.

“At the moment, the system of in-person voting means it just involves the members who can afford to book a hotel and take some days off work – it’s quite self-selecting. This has always been the case, but it’s more disproportionate now it’s not 1,000 people out of 68,000, but 1,000 out of 230,000.”

Another party figure said there was an increasing acceptance that the system needed to be looked at: “When you have 0.05% of members making the policy decisions, things need to change. We all know that.”

While Greens argue that its member-led system allows for a broad base of views, the ability of grassroots members to suggest policy can cause controversies, such as a motion at the spring conference in March that sought to commit the party to the view that “Zionism is racism”.

The motion was delayed because of procedural and technical difficulties, but could return for the autumn conference in October.

Officials point out that as with many current difficulties in the party, much of it problem comes from a lack of resources to cope with so many members, although this is gradually changing as the Greens’ financial position improves.

The logistics of Green party conferences have been organised by the same single person for about 20 years – only this year do they have a team to help.

Some senior Greens also argue that Polanski has been too focused on broadcasting the party’s message to devote enough time to improving internal structures, which will be necessary to win more council and parliamentary seats.

“The leader is traditionally a spokesperson rather than the sort of leader you get in other parties, and I think Zack sometimes hides a bit behind that in not making decisions,” one said. “But at the same time, it is a big task, and there is only one of him.”

Another discussion among senior Greens is whether this leadership model could also be outdated for a party that is so numerically large and polling as high as 19% nationally.

Until 2008, the Greens had what were known as “principal speakers” rather than leaders, and even now the leader has very limited powers, with just one vote among about two dozen members of the party’s executive committee.

Some Greens argue this does not give sufficient flexibility even for a leader with a mandate like Polanski’s – he won almost 85% of members’ votes – to make choices on policy, having to wait for the next conference.

One senior figure said: “There has to be a balance in terms of the policies set by conference, and some trust and leeway given to the leader, along with ways to hold them to account if needed. It would help the party be more agile.”

Others dispute that. One party official said Polanski, who routinely expresses opinions on broadcast interviews and social media, has the ability “to make an interpretation of core values while responding to events as they unfold”, and that Green members would object if he went too far.

Another decision also faces the Greens: while they won the Gorton and Denton byelection, and have hopes in the vote for Greater Manchester mayor, how should they best respond to Andy Burnham as prime minister?

One party figure said: “We have to think properly about this, and how we continue to make ourselves distinctive. We have done well from being a more personable and hopeful option to the left of Keir Starmer, and that role might be about to be filled by Burnham.”