TRANSGENDER women will be banned from becoming members of the Women's Institute from April next year.
The decision has been taken "with the utmost regret and sadness", the organisation said, adding that it retains the "firm belief that transgender women are women".
The National Federation of Women's Institutes (NFWI) said it had made the policy change in the wake of the Supreme Court ruling earlier this year on biological sex.
The NFWI news comes a day after Girlguiding announced it has banned trans girls from joining.
NFWI chief executive Melissa Green said many members will find the decision "extremely painful", and it is understood some transgender members have been contacted to explain the reasons for the change in policy and be assured of support going forward.
Trans rights activists in Edinburgh (Image: Jeff J Mitchell)
Although, similar to Girlguiding, the NFWI said it does not hold data on how many of its members are transgender.
Green said: "It is with the utmost regret and sadness that we must announce that from April 2026 we can no longer offer formal membership to transgender women.
"As an organisation that has proudly welcomed transgender women into our membership for more than 40 years, this is not something we would do unless we felt that we had no other choice.
"To be able to continue operating as the Women's Institute, a legally recognised women's organisation and charity, we must act in accordance with the Supreme Court's judgment and restrict formal membership to biological women only.
"However, this change is only in respect to our membership policy and does not change our firm belief that transgender women are women."
The NFWI said while it can no longer "legally offer formal membership to transgender women" after the Supreme Court ruling, the organisation will "bring forward programmes to continue to extend fellowship, sisterhood, and support to transgender women".
Campaigners from For Women Scotland (FWS) outside the Supreme Court in London (Image: PA)
Green said it will launch a "national network of local WI Sisterhood groups, which will offer monthly opportunities for all people, including transgender women, to come together to socialise, learn from each other, and share their experiences of living as women" from April 2026.
Trans rights campaigners claimed this week that Girlguiding was "being forced to exclude young trans girls by adults with bigotries and institutional power".
TransActual described the Girlguiding policy change as "yet another horrible act of violence against the most vulnerable trans people".
The Trans+ Solidarity Alliance called on the Government to "ensure clarity for organisations on how to remain trans-inclusive, rather than leave them at the mercy of anti-trans lawfare forcing them to betray their own values".
The group's founder Jude Guaitamacchi said: "Imagine being a group that has welcomed trans members for generations being told who you can and cannot associate with, regardless of the wishes of the group itself. It's cruel and a failure of this government to protect human rights, including freedom of association."
A trans rights campaigner is surrounded by campaigners from For Women Scotland (Image: PA)
Organisations are still awaiting new transgender guidance produced by equalities watchdog the Equality and Human Rights Commission (EHRC), which is being assessed by the Government.
Ministers have had the guidance for three months but have vowed not to "rush" publication of a proposed code of practice which will be used by businesses and other organisations to inform their provision of single and separate-sex services such as toilets and changing rooms.
The guidance requires ministerial approval and would only come into force 40 days after the Government had laid the draft code in Parliament.
The EHRC wrote to Women and Equalities Minister Bridget Phillipson in October, urging her to hurry up with bringing in the new guidance, saying some organisations were currently using unlawful practices.
The code has not been updated since 2011 and the latest draft has been produced in the wake of the Supreme Court ruling, which stated that the words "woman" and "sex" in the Equality Act 2010 referred to a biological woman and biological sex.