Maureen Colquhoun, who has died aged 92, was the Labour MP for Northampton North from 1974 to 1979 and a crusading politician whose radical feminism was so far ahead of her time that it destroyed her parliamentary career. Although she lost her seat in a general election, she had effectively already been disavowed by the Labour party after coming out as a lesbian. She was the first MP to take such a courageous step, while publicly acknowledging at the time that in doing so she had ruined her chances of remaining in the House of Commons. (The first male MP to come out as gay was Chris Smith, in 1984.)

She was ridiculed in the press, harassed in public and mocked by fellow politicians for the determined stance she took on a wide range of issues to advance women’s rights. “We in parliament, who believe in making life better for women … believe that our aims must be translated into laws, which will be binding not merely on the present government but on future governments,” she told the Commons in 1975, when introducing an ill-fated private member’s bill to require equal representation for women in government appointments to public bodies. “That is what I consider I am here for.”

Among the many issues for which she campaigned were the abolition of women’s prisons, abortion on demand, creche facilities at political conferences and the decriminalisation of prostitution, to which end she introduced the unsuccessful protection of prostitutes bill in 1979. When she asked the then Speaker, George Thomas, to address her as “Ms” in the Commons, her initiative was derided with the newspaper headline “When a Ms Is As Good As a Male”.

Hers was a brave and lonely battle. But throughout her life she exhibited a readiness to challenge and confront entrenched opinion on anything, regardless of the impact she might make and the evident danger of thus alienating even her own colleagues, at Westminster and in her constituency party. She told the author Helen Lewis, in an interview for her recent book Difficult Women, that she knew she was “tiresome” because she refused ever to apologise for her views or her sexuality, but remained happily unrepentant.

She also disclosed to Lewis that in 2017, decades after her tumultuous five years as a Northampton MP, she received a long letter of apology from the constituency acknowledging “the very great contribution” she had made, the pioneering role she had played, the courage she had shown and her remarkable record of public service.

In 1977 she had been deselected as the MP by the Northampton North party, on a spurious pretext that was subsequently withdrawn, and was only reinstated as the party candidate in the 1979 election after an appeal to Labour’s national executive committee. But it was too late to rescue her reputation with the voters and in the election that brought the first woman prime minister into office, she lost to the Conservative candidate, Tony Marlow, on a swing of 8% – a significant three points higher than the national swing away from Labour.

She was raised single-handedly by her Irish mother, Elizabeth Smith, in Eastbourne, East Sussex. Maureen was educated at a local convent, a commercial college in Brighton and then at the London School of Economics. In 1949, aged 20, she married the journalist and author Keith Colquhoun, with whom she had three children.

She worked variously as a civil servant, a literary research assistant and in an art gallery in Shoreham, West Sussex. She had joined the Labour party in 1945 and embarked on her political career on Shoreham urban district council in 1965, winning election as one of only three Labour councillors and the only woman on the council.

All her life, Colquhoun was in the news. In Shoreham she made a name for herself as a councillor when she was briefly banned from council committee membership as a “chatterbox”. On one occasion, dissatisfied with her mother’s health treatment, she locked herself and her mother in a doctor’s surgery and telephoned the local newspaper. On another she protested outside a Conservative parliamentary selection meeting in Arundel because they were interviewing the candidates’ wives.

She stood as the Labour candidate in Tonbridge, Kent, in the 1970 general election, in which the Conservative MP secured the largest majority in the constituency since the 1930s. She was then somewhat unexpectedly elected for the newly created seat of Northampton North in February 1974. The Labour MP for the previous Northampton constituency, Reginald Paget, had retired. She increased her majority in the second 1974 election.

She met Barbara Todd, known as Babs, who would become her partner and wife, in 1975. Todd, who had earlier moved back to the UK from the US with her two daughters after leaving her husband, then worked for the lesbian organisation Sappho as co-editor of its magazine and the couple met in connection with Colquhoun’s balance of the sexes bill. They set up home together, and this was disclosed by Nigel Dempster in the Daily Mail, Colquhoun readily acknowledged her change of circumstance, commenting: “The day hasn’t yet arrived when an MP can be unseated by a gossip columnist.”

She proved to be only partly correct. When she was deselected, her local party chairman was reported widely as saying: “She was elected as a working wife and mother … this business has blackened her image irredeemably.” In the Guardian, Polly Toynbee questioned whether such a move would have been made “had she still been quietly married”, but Colquhoun told Woman’s Own in 1977: “Being a lesbian has ruined my political career.”

When she left Westminster, Colquhoun worked for Gingerbread, the charity for single parent families, from 1980 to 1982. She then returned to the Commons to work as a research assistant for a Labour MP and was an active member of the Secretaries and Assistants’ Council, campaigning for better pay and conditions for parliamentary staff.

She had stood down as a local councillor and a West Sussex county councillor when elected to parliament, and resumed her local government career in 1982. She was a member of Hackney council until 1990, and when she and Todd moved to the Lake District she became a councillor on Lakes parish council (1994-96, 2006). She was also an appointed member of the Lake District national park authority from 1998 to 2006 and a busy local activist.

Maureen and Keith were divorced in 1980. In 2015 she married Barbara, who died last year.

Colquhoun is survived by her three children, Andy, Mary and Eddy, by Barbara’s daughters, Mairi and Hilda, and by six grandchildren and five great-grandchildren.

• Maureen Morfydd Colquhoun, politician, born 12 August 1928; died 2 February 2021

• This article was amended on 9 February 2021 to clarify that the Labour MP Reginald Paget retired from the constituency of Northampton in 1974 and did not contest the Northampton South seat in the general election of February that year, as an earlier version had it. Barbara Todd was a citizen of the UK rather than the US, as previously stated.