Four Labour-affiliated trade unions will boycott the 2026 Labour Women's Conference after the party decided to bar trans women from the main hall, deepening a rift between the party leadership and its union base over how to comply with the UK Supreme Court's ruling on biological sex.

Unison, Usdaw, Aslef and the Musicians' Union confirmed they will not attend the conference, scheduled for Liverpool on the eve of the main Labour Party conference in September 2026. The Metro first reported the boycott on 29 July 2026, with PinkNews following on 30 July (Metro; PinkNews).

Labour MP Kate Osborne publicly pledged the same day to join the boycott. In a post on her official Facebook page on 30 July, Osborne said she would be "joining my union comrades" in staying away from the Liverpool event (Facebook).

The boycott stems from a decision Labour announced in December 2025, when The Guardian reported that trans women would be barred from the main part of the 2026 women's conference (Guardian). The ban applies to the main hall but not to fringe meetings — the smaller, informal sessions that run alongside the official proceedings. Labour said the restriction is the least restrictive way of balancing accessibility with compliance under equalities law.

That legal framework shifted in April 2025, when the UK Supreme Court unanimously ruled that, under the Equality Act, a woman is defined by biological sex. The Equalities and Human Rights Commission (EHRC), the statutory body that enforces equality law in Britain, subsequently issued guidance interpreting the ruling as meaning a trans woman is a biological male who identifies as a woman and should not use single-sex spaces.

Labour cancelled the 2025 Women's Conference outright in the immediate aftermath of the Supreme Court judgment. A leaked National Executive Committee (NEC) advice paper — the NEC being Labour's governing body — recommended delaying the conference because the only legally defensible alternative was to restrict attendance to biological women. The NEC subsequently agreed that references to "woman" or "women" in party rules must be interpreted on the basis of biological sex.

The conflict with the unions is rooted in longstanding policy differences. Unison's policy states that trans women are women, trans men are men, and non-binary identities are valid. The union is actively campaigning for a change in the law to align with its trans equality stance. The BBC understands that the trans ban goes against long-standing policies on trans inclusion in most Labour-affiliated unions, and that a mass boycott could result.

Historically, Labour allowed people to self-identify, meaning trans women could attend the women's conference and participate in all-women shortlists — the mechanism the party uses to select candidates in certain seats to increase female representation. The annual conference brings together hundreds of women, including MPs, councillors and supporters.

The broader context is a party caught between a statutory obligation it says it cannot avoid and a trade union movement whose policy positions were forged when self-identification was the operative convention within the party. The NEC's leaked advice paper made clear that party lawyers saw no legally defensible middle ground: either delay indefinitely or restrict to biological women. The compromise reached, restricting only the main hall while leaving fringe meetings open, has not satisfied the unions whose policies explicitly affirm trans women as women.

For Labour, the immediate question is whether the four confirmed boycotters remain isolated or whether the BBC's understanding of union sentiment proves correct and further affiliates follow. The conference structure, which relies on union delegations for both attendance and procedural weight, would be materially weakened by a mass walkout. The decision by Osborne, a sitting MP, to align publicly with the boycotting unions adds a parliamentary dimension to what might otherwise have remained a movement-level dispute.

The episode also illustrates the pace at which the Supreme Court ruling is reshaping institutional practice across the Labour movement. Less than sixteen months separate the April 2025 judgment from the September 2026 conference. In that window, the party has moved from cancellation, through a leaked legal assessment, to a policy that its own affiliates consider incompatible with their constitutions.