As she was growing up in a closely knit Jewish family in the East End of London, poverty and fatherlessness shaped the radical spirit of my mother Bertha Sokoloff, who has died aged 98. Her memory of the Battle of Cable Street anti-fascist demonstrations in 1936 was vivid. Family history held that her apolitical sister, Faye, got arrested as a bystander, whereas Bertha, chalking slogans and running errands, and already a member of the Young Communist League, was not.

Bertha was born in Whitechapel, third of four children of Rachel and Jacob Markovitch, immigrants from Romania. Jacob was injured in army training during the first world war; he began a relationship with one of his nurses and later abandoned his family. Rachel struggled to bring up her children with help from Jewish charities.

From Robert Montefiore elementary school, Bertha gained a scholarship to Central Foundation girls’ school in Spitalfields. She left unwillingly at 16, and became a secretary at the Royal Institute of International Affairs, then for Gollancz publishers, and at Stepney borough council. She married Stan Sokoloff, a fellow Young Communist, in 1940. They counted themselves lucky that he survived four years’ second world war service in Africa and she weathered the London blitz.

Facebook Twitter Pinterest Bertha Sokoloff, second right, in 1945, celebrating the victory of Phil Piratin, the Communist MP, who is standing behind Clement Attlee. Photograph: Bettmann

During the war, Bertha proved an able branch secretary for the Communist party in Stepney at a time of growth. In 1943 she took up war work in a factory where the management noticed she was clumsy on machines but good at maths and at inspiring others: they made her a productivity officer. Bertha was the agent for Phil Piratin who was elected to parliament as the UK’s second ever Communist MP in 1945, and she was elected as a Stepney councillor that year.

In 1949, Bertha and Stan, with two young daughters, me and my sister, Ruth, moved from a condemned East End flat to council housing in south London. She left “the party” in 1957 over the Soviet Union’s invasion of Hungary. However, through community-building in St Paul’s Cray, helping to run a campaign for a nursery at Woolwich College, volunteering as a housing adviser in Bromley after retirement, or protesting in 2013 against the closure of Pocklington House, a home for the blind in Northwood where she lived, Bertha was an effective and respected activist all her life.

After teaching in infant schools, Bertha graduated in sociology in 1971 at the same London University ceremony as her younger daughter. She loved teaching mature students at Woolwich College in the 1970s, and after retirement enjoyed spending time with her five grandchildren. An atheist but culturally Jewish, in old age she contributed to the social life of Bromley Reform Synagogue.

Never happy with historians’ interpretations of East End communism, she wove her own experiences into a book about the dedicated community worker Edith Ramsay (Edith and Stepney: 60 Years of Education, Politics and Social Change, 1987). Her gift for friendship lasted to the end of her long life.

Stan died in 2005. Bertha is survived by her daughters and grandchildren.