Scotland’s new citizens’ assembly will recruit its members by going door to door across the country in order to reflect a diverse range of views of over-16s, and the assembly will not ask directly about independence in an attempt to escape the binary constitutional debate.

Giving their first joint press conference on Tuesday, the co-conveners, David Martin and Kate Wimpress, moved to rebuff criticism that the plans represented an expensive talking shop to further the nationalist cause, as they revealed a detailed set of target quotas across views on independence, Brexit and party politics.

Teams of recruiters expect to knock on thousands of doors across Scotland before October in order to complete what organisers admit is a “challenging” random selection process, using face-to-face screening interviews to recruit a “mini-public” of about 120 people who reflect a spectrum of the over-16 population in terms of location, age, gender, ethnicity, disability, education and viewpoint.

Describing the door-to-door recruitment as “old school”, Wimpress said she hoped the framework set out on Tuesday would undercut assumptions of pro-independence bias. The target quotas include 40% in favour of independence and 45% opposed, along with 56% in favour of remaining in the EU and 30% who want to leave. On Holyrood voting intention, the targets are 30% of the membership supporting the SNP, 18% Scottish Conservative and 16% Scottish Labour.

The figures, which are a little lower than the current levels of support for the SNP and independence, were arrived at by averaging all polling with samples in Scotland conducted between August 2018 and August 2019.

Before the briefing, Martin addressed accusations from the Scottish Conservatives that the assembly was “an SNP vanity project”.

“I’m not naive: it is good for the Scottish government to get an ongoing discussion on the constitution. On the other hand, they are taking a massive risk because the government has no idea what’s going to come out at the end of this process,” he said.

The former MEP, who represented Scottish Labour in Brussels for 35 years, said: “I only agreed to take this on because I got the assurance that we would be independent of government.”

Some critics suggest that the project has been mishandled from the start. The first minister, Nicola Sturgeon, announced it in April alongside a package of measures to prepare for a second independence referendum, which the Scottish Liberal Democrat leader, Willie Rennie, said made it impossible to have confidence in the assembly.

Martin agreed this was a mistake on Sturgeon’s part. But he was critical of threats from the Scottish Tories and Lib Dems to boycott the process, accusing them of “playing games”.

Much of the framework for the assembly draws on the Irish experience of using citizens’ assemblies to reach consensus on abortion and same-sex marriage.

Professional mediators with no links to political organisations will facilitate each of the six weekend meetings. These will be livestreamed, any documents submitted will be available to the public, and there will be space for the media to observe.

The Scottish version will also pay members a “gift” of £200 a weekend, after organisers in Ireland found that people with caring responsibilities and poorer people dropped out at a higher rate because their involvement became too burdensome financially.

At the briefing on Tuesday, Martin confirmed that the publicly available details of participants would be limited to full name and geographical location. He acknowledged that the final membership could include those with criminal records or extreme views: members will be required to sign up to a code of conduct and will be relied upon to confirm there is nothing in their background that could bring the assembly into disrepute.

Martin said: “If you end up with the chattering classes then it has not served its purpose. And you also have to be sure that no matter how articulate people are, their voice is heard equally. That’s the point of the facilitators, to ensure that no one dominates.”

Martin wants people to come in with an open mind, call on experts and then draw conclusions from what they hear. Narrowing down the initial question posed by Sturgeon – what kind of Scotland would we like to live in, how is it affected by Brexit and what are the implications of that? – he envisages more “manageable” subjects such as fairness at work and freedom of movement.

The Scottish government has committed to producing an action plan within three months of the assembly’s report being put before Holyrood for scrutiny and debate.

Martin said he hoped the process would be a healing one, not just for the 120 or so people directly involved but for the wider community as well. It was “vital for democracy” after two highly divisive referendums, Martin said. “In Scotland and the UK we are now in the position where a lot of people just do not tolerate other people’s points of view.”