A Tasmanian group that has been accused of sharing "anti-transgender" material on social media has been invited to take part in designing trans-inclusionary posters for public bathrooms.

The motion to introduce the posters, which was moved by alderman Holly Ewin, was approved by the full Hobart City Council last month.

In the motion, the wording and content was to be "developed in collaboration with relevant organisations, such as Working It Out and Transforming Tasmania".

But on Thursday night an amendment to include self-described radical feminist group Women Speak Tasmania in the design process was voted through, frustrating transgender advocates who have labelled the group "trans exclusionary".

Hobart City Council Councillor Holly Ewin proposed the posters for public toilets in the Tasmanian capital. ( ABC News: Peter Curtis )

Councillor Ewin, who identifies as non-binary and chooses to use the pronouns they and their, said they could not understand why other aldermen wanted Women Speak Tasmania included in the design of the posters.

"I guess from their [the aldermen's] perspective it's in the interests of balance and impartiality," they said.

"[Women Speak Tasmania is] just an anti-trans group posting anti-trans sentiment."

They said Thursday night's meeting made it clear Women Speak Tasmania was trans exclusionary.

"They [Women Speak] flat out think trans people shouldn't be using public restrooms unless they're using non-gendered bathrooms or the sex that they were assigned at birth," they said.

Martine Delaney is against Women Speak Tasmania being involved. ( ABC News: Rhiannon Shine )

Transgender advocate Martine Delaney described the decision as farcical.

"It smacks of somebody trying to ensure that there isn't actually a poster at the end of it," she said.

She said she could not possibly see how it could be helpful to have the group involved in the design process.

"Women Speak, despite repeatedly making claims that they are supportive of trans people and have no problems or issues with trans people or trans rights, almost every action they take is designed to belittle trans people, question the existence of trans people and exclude them wherever possible," she said.

"I can't see how one would get through such a process and come out of it with a poster that is at all inclusive."

Some of the images from Women Speak Tasmania's Facebook page. ( Facebook: Women Speak Tasmania )

In a letter sent to aldermen on Thursday, Women Speak Tasmania wrote: "Councillor Ewin's proposal has the effect of encouraging the mixed sex use of all toilet and changing room facilities."

Alderman Damon Thomas, who moved for Women's Speak Tasmania to be included, said the group clearly has an interest and contribution to make in the debate.

He said the decision to include the group was "a no brainer".

"They didn't have an issue about a poster. They do have an issue about not having an ability to contribute to what the posters say," he said.

Isla MacGregor from Women Speak Tasmania says the group is not "anti-trans" . ( Supplied )

Isla MacGregor from Women's Speak Tasmania rejected the assertion the group is "anti-trans."

She said the group supports the protection and safety of transgender people as well as women and girls, but she does not think "trans women are women".

"The vast majority of women in our community want to maintain single sex services and facilities based on the biological reality that persons with male genitalia are not what women wish to be exposed to in single sex facilities," she said.

"I think organisations like Transforming Tasmania and other groups understand that when we're discussing issues about single sex services, we have to be considerate of multi-faith communities, some of which have got very strong restrictions on sharing spaces with male-bodied people."

She said she genuinely hopes to come to an agreement about the posters.

"What we don't support is the sort of signage that Holly Ewin is providing," she said.

"What we would like to see is a rotational poster … supporting diversity in all its forms."

The full council will need to vote on the amendment later this month.