Forster [née Mackenzie], Jacqueline Moir [Jackie] (1926–1998), journalist and campaigner for homosexual rights, was born on 6 November 1926 at the Royal Northern Hospital, Upper Holloway, London, the only daughter and eldest of two children of Kenneth Pirie Mackenzie, a doctor and major in the Royal Army Medical Corps, and his wife, Margaret Rutherfurd Alexander (d. 1961). She spent her early years in India, where her father was stationed, then moved to Scotland, and was educated at St Leonard's School, Fife, and Wycombe Abbey, Buckinghamshire. She gained theatrical experience touring in repertory (1945–50) and had a brief film acting career before moving into television. There she worked with Gilbert Harding as a reporter and was soon recognized for her spirited presentation. In 1956 she won a prix d'Italia for her coverage of the marriage of Grace Kelly to Prince Rainier of Monaco; her own series followed. She returned to acting in the television sitcom Trouble for Two (1958), but reportage was her forte and she graduated to the news programmes Tonight, Panorama, and Late Night Extra.

On 15 February 1958 she married Peter Currie Forster (b. 1925/6), an author and journalist. She began travelling to the USA to make television programmes, and it was there, in 1958, that she had her first lesbian experience. This clandestine relationship, with an American journalist, lasted until 1961.

Following her divorce in 1962, Jackie Mackenzie travelled to Canada where, on a lecture tour in 1964, she met Barbara Mary (Babs) Todd, née Thomas (b. 1933), an actress. They lived together in Toronto, Massachusetts, and London with Todd's two daughters whom they raised together. They separated in 1975 but the daughters continued to regard Mackenzie as their stepmother.

Although she returned to journalism, working for Border Television and writing regular columns for She and the Sunday Express, MacKenzie became increasingly incensed at the prejudice which forced gays and lesbians into a ‘closet’ existence. She was soon active in the movement for homosexual equality and (now using the name Jackie Forster) ‘came out’ in 1969 when she made an impassioned speech at a Speakers' Corner meeting of the reformist Campaign for Homosexual Equality.

As the gay liberation movement developed, Forster switched her allegiance to the more radical Gay Liberation Front, and in 1971 she took part in the first Gay Pride march. An involvement with Arena-3, the first British lesbian magazine of the modern era, developed into her founding, with Todd, the networking lesbian organization Sappho with its eponymous magazine, which she edited for ten years (1971–81).

As a member of Women in Media, Forster acquired techniques of lobbying for change at the side of fellow journalists Anna Raeburn, Mary Stott, and Jill Tweedie. Such action was inspired by trade-union tactics rather than by lesbian bar culture, although the latter remained a vital sector of Forster's constituency: it was at Sappho's monthly meetings that, with glass in hand and a willing ear, she provided friendship and guidance to women who kept a low profile by choice and those who were forced to keep a low profile through circumstances. Sappho's guest speakers were impressive, ranging from Helena Kennedy and Maureen Duffy to Lord Longford, and members debated issues as apparently removed from lesbian cultural concerns as the death penalty and nuclear disarmament.

Her early forays into the arena of debate with the Campaign for Homosexual Equality, Kenric (the lesbian support and social organization), and the Minorities Research Group made Forster a natural recruit for the Greater London council's women's committee in the 1980s; there she provided a constant, prodding presence and was never afraid to speak her mind even when her opinions clashed with the socialist status quo. Later she took part in direct action, participating in sit-ins at homophobic pubs and radio stations and aligning herself with Outrage, the gay and lesbian pressure group.

Forster was at the forefront of many campaigns. When she organized help for lesbians to conceive children via artificial insemination by donor she was vigorously attacked by some elements of the press. She remained a champion of lesbian motherhood and, with Gillian E. Hanscombe, co-authored a book on the subject, Rocking the Cradle (1981). Hanscombe called her 'a rare individual. She has noble instincts and the noblest of them is to fight for justice of any kind, not just for lesbians' (Woodis).

In confrontational situations Forster's earthy humour often carried the day. She persisted in engaging publicly in the fight against injustice, whether discussing the London lesbian and gay policing initiative or drawing attention at a civic reception to the sexist differential affecting the pay of the men and women employed there as waiters. She campaigned for the Sex Discrimination Act (1975) and the creation of the London Women's Centre (of which she was a director, 1992–6), was a curator of the Lesbian Archives, and was involved with gay medical and social workers' organizations. She also taught drama in prison.

A founder member of the Women's Broadcasting and Film Lobby, Forster became the archetypal 'rent-a-dyke' whenever a ‘lesbian quote’ was required (Woodis). She featured in London Weekend Television's Speak for Yourself (1974), the first lesbian and gay access television programme, and 'From High Heels to Sensible Shoes' (1997) in the BBC series The Day that Changed my Life; the same year the National Film Theatre devoted an evening to her work at which she appeared in conversation with the writer Rose Collis.

For over two decades MacKenzie's slogan, 'What about the women?' was as familiar as her gold cigarette-holder and the sound of her rich, fruity voice. She had once been a prospective Liberal candidate for Cheltenham, but she abandoned conventional politics in favour of lesbian feminist activism and, furthermore, did so at a time when lesbian concerns were still marginalized by an emerging women's movement. By establishing Sappho, the magazine and the organization, she provided an important forum and 'probably saved a lot of isolated lesbians under plain brown wrappers' (Wilmer, Visions of liberty).

In 1993 Forster was diagnosed with breast cancer but recovered and, typically, campaigned to raise awareness of the disease. She remained active in journalism as a voluntary editor with Talking Newspapers for the Blind while earning a living working in London for the British School in Rome. In 1995 she founded Daytime Dykes, a social group whose focus—visiting historical buildings and museums—contrasted somewhat with that of her carousing days but which nevertheless continued to perpetuate lesbian solidarity. In 1993 she began a relationship with an actress known as Lace, which lasted until her death. She died on 11 October 1998 at Guy's Hospital, London, from emphysema.