Before she had established herself as a significant presence on the orthodox stage, Gillian Hanna, who has died aged 75 from an autoimmune disease, worked with the socialist theatre groups 7.84 and Belt and Braces. On one occasion during the 1970s heyday of fringe theatre she found herself with a number of female actors, all auditioning for the same small role with Belt and Braces. Gillian decided that enough was enough.

Thus in 1975 she, Chris Bowler and Mary McCusker founded Monstrous Regiment (echoing John Knox’s tract against rule by female monarchs), with the aim of reflecting more fully the lives of women. Of their first production, Scum: Death, Destruction and Dirty Washing (1976), by Chris Bond, Claire Luckham and the company, set in the Paris Commune of 1871, Gillian wrote: “The shivering excitement in the air was almost tangible. Women felt they were throwing off the shackles of a thousand years or more and finding freedom. We were going to be the midwives for a whole new era of equality.”

There followed 15 years of challenging, dangerous, rebellious and always entertaining productions of new plays by 32 writers, including Caryl Churchill, Robyn Archer, Michelene Wandor – and lucky me, with Calamity (1983) and Origin of the Species: A Love Story (1984), produced with Birmingham Repertory Theatre, their first co-production with a mainstream theatre. The common denominator was that our plays should deal with women’s experience and always have a cast of more women than men.

In the early 1980s Gillian displayed her flair for translation in Monstrous Regiment’s selection of foreign plays: from Italy, Dacia Maraini’s Dialogue Between a Prostitute and One of Her Clients and Franca Rame and Dario Fo’s The Fourth Wall; and from France, Théâtre de l’Aquarium’s Shakespeare’s Sister. Her one-woman performance of her translation of Rame and Fo’s A Common Woman (1988-89) brought her a Time Out best actress award. She told the story of the whole venture in the book Monstrous Regiment: Four Plays and a Collective Celebration (1991).

Her range included roles as diverse as the demon barber’s accomplice, Mrs Lovett, in Stephen Sondheim’s Sweeney Todd (Half Moon theatre, London, 1985); Martha in Who’s Afraid of Virginia Woolf? (Crucible, Sheffield, 1988); the Nurse in Romeo and Juliet (Royal Exchange, Manchester, 1992); and Zinaida in Ivanov, directed by Katie Mitchell (National Theatre, 2002). She was in the West End production of The House of Bernarda Alba with Glenda Jackson and Joan Plowright (1986); played the Queen Mother in a royal family exiled to a council estate in Sue Townsend’s The Queen and I (Royal Court and then Vaudeville, 1994-95); and was the aunt to Daniel Radcliffe’s disabled young man in Michael Grandage’s West End and Broadway productions of Martin McDonagh’s The Cripple of Inishmaan (2013-14).

Gillian Hanna in Scum: Death, Destruction and Dirty Washing, 1976. Photograph: Roger Perry

Her final stage role came as a splendid Grandma in my version, following the Monstrous principle of more roles for women, of Robert Louis Stevenson’s Treasure Island for the National Theatre (2014-15). Again, lucky me.

On television, she played Margaret Knight, the mother of a teenager jailed in an adult prison who took his own life, in The Life and Death of Philip Knight (1993), based on a true story. In the Channel 4 soap Brookside (1995) she was Brenna Jordache, sending hate mail and championing her abusive brother Trevor, killed and buried under a patio.

Her film credits included Les Misérables (1998), All the Queen’s Men (2001), a gloriously nasty Mrs Sowerberry in Roman Polanski’s Oliver Twist (2005) and Mr Nice (2010). In her final film, Genius (2016), directed by Grandage, she played Julia Wolfe, mother to Jude Law as the US novelist Thomas Wolfe.

Born in Buxton, Derbyshire, and brought up in Thornton Heath, Surrey, Gillian was the elder daughter of Irish parents, John Hanna, a GP, and Vera (nee Bryans), a pianist and singer. At Beresford House school, Eastbourne, she became head girl. As a child she spent holidays in Ireland, and she returned there to study at Trinity College Dublin, where she played in numerous student productions, including Lady Bracknell in Oscar Wilde’s The Importance of Being Earnest. In 1967 she graduated with a first-class degree in modern languages. She had planned to be a simultaneous translator, but was immediately invited to play Mrs Sullen in The Beaux’ Stratagem at the Gate theatre, Dublin, and so her professional stage career got under way. Work at the Liverpool Everyman and Newcastle University theatre followed, and then the experimental world of the fringe.

Of her translations outside Monstrous Regiment, that of Fo’s The Accidental Death of an Anarchist was used in a successful production in London at Wyndham’s theatre (1980). She worked extensively with the Royal Court’s international programme’s summer school for playwrights, and in 2013 her translation of Fausto Paravidino’s They Came Into My Field was performed at its international festival.

Gillian Hanna as Grandma and Patsy Ferran as Jim Hawkins in Bryony Lavery’s version of Treasure Island, after Robert Louis Stevenson, at the Olivier, National Theatre, 2015. Photograph: Alastair Muir/Rex/Shutterstock

Gillian and Diane Gelon, a lawyer, entered into a civil partnership the day after the arrangement became legal, in 2005. They also married in Diane’s native California in 2008, and had three wedding parties – Gillian loved parties. In all, Gillian and Diane lived together for 37 years, in London and in Dungeness, on the Kent coast, where with the architect Simon Conder they created an extraordinary home.

Warmth, incisive intelligence and huge generosity of spirit characterised both Gillian’s acting and her mentoring of younger actors. In her final days she was keen to see her family, colleagues and many friends.

She is survived by Diane, her sister, Sara, her nieces, Joanna and Rebecca, and grandchildren, Alexis and Jacob.

• Gillian Hanna, actor and translator, born 20 July 1944; died 18 August 2019