George Brandis will meet LGBTI groups on Thursday to discuss the same-sex marriage plebiscite in a last-ditch consultation before Labor decides its final position on the nonbinding vote next week.

Marriage equality advocates who are opposed to the plebiscite under any circumstances have expressed concern the meeting is intended to fashion compromise to pass the nonbinding vote.

The consultation was organised by the attorney general through Australians For Equality (A4E), the group developing campaign capacity to fight the yes case in the event the plebiscite goes ahead.

At a meeting on 26 September Labor refused to nominate conditions that would be sufficient to win its support for a plebiscite and the Coalition refused to nominate changes it could offer.

The shadow attorney general, Mark Dreyfus, told Guardian Australia he would meet LGBTI groups on Friday following Brandis’s meeting with the groups on Thursday.

“Four or five months ago there was some equivocation in LGBTI groups but now they’ve squarely lined up and they’re uniformly against plebiscite,” he said.

When the specific proposal for the plebiscite was released, a broad coalition of LGBTI groups including A4E and Australian Marriage Equality rejected it in a joint statement.

Long-time marriage equality advocate, Rodney Croome, said he expected Brandis would “seek points of compromise to breath new political life into a plebiscite, just as he did with Mr Dreyfus”.

Compromises including ditching the $15m in public funding and making the result of the plebiscite self-executing could help win support from some LGBTI groups, but several groups attending the meeting told Guardian Australia they would reject a plebiscite under any circumstances.

Croome said he was “optimistic the LGBTI groups at the meeting will not endorse any compromise”, citing surveys that show the LGBTI community does not want a plebiscite under any circumstances.

In comments published on SameSame, Croome noted the joint statement describing the plebiscite as “unfair, unjust and unworkable” left the door open to possible compromise if the proposal were modified to address concerns.

LGBTI rights campaigner Kate Doak, who signed the joint statement and is a member of the New South Wales marriage equality steering committee, said some marriage equality advocates “would be some willing to negotiate if it’s shown to be in good faith”.

“A lot want to see this thing done. It’s reached fever pitch and a toxic level of debate already ... a lot are just going ‘right let’s get done one way or another’.”

GetUp, the NSW Gay and Lesbian Rights Lobby, Rainbow Families Victoria and Transgender Victoria said they would not accept a plebiscite under any circumstances.

The Get Up marriage equality director, Sally Rugg, told Guardian Australia “there are no circumstances where Get Up would a support a plebiscite”.

“Our members’ main concern is the harm to the LGBTI community and the fact it is alien to representative democracy, – neither of those can be alleviated,” she said.

NSW Gay and Lesbian Rights Lobby co-convenor Chris Pycroft said: “Our position is absolute – we are against the plebiscite.”

Victorian Gay and Lesbian Rights Lobby co-convenor, Rachael Hambleton, said: “There are currently no foreseeable circumstances in which we would support a plebiscite.”

The Victorian gender and sexuality commissioner, Rowena Allen, will not attend the meeting but expressed absolute opposition to the plebiscite.

“I’ve got faith in people – I know that the plebiscite is not good for our community and I’m quite confident that’s the message Brandis will get,” she said.

The Australian Marriage Equality chairman, Alex Greenwich, said it was “proud” to have facilitated the meetings which would be the largest consultation with the LGBTI community in his 10 years of advocacy.

“We see these meetings as an opportunity for all parties to hear from others in the community and to work together to achieve marriage equality in this term of parliament,” he said.

“We have made it clear in every meeting with every politician that we don’t support a plebiscite.”