Una Kroll, who has died aged 91, was a doctor, a nun, a feminist campaigner with a prominent role in the movement for the ordination of women, an activist for peace and justice, counsellor to many, and to many others a disturber of the peace. She defied labels. Perhaps the title of her 1995 book, Vocation to Resistance, came closest to defining her.

Never afraid of publicity, she courted it when the General Synod, the legislative body of the Church of England, in 1978 said no to women’s ordination. Una called down from the gallery: “We asked for bread and you have given us a stone.” Her words echoed far beyond Church House. It was, she said, “all part of my non-violent resistance to injustice”. Her 2014 autobiography would be titled Bread Not Stones.

In 1992 the first women were ordained in England. Una was by then living in Wales, and when the Church in Wales followed suit in 1997 she was made a priest. However, something of the spiritual enfant terrible of her youth remained. She shocked her admirers and friends by making the ultimate surrender of personal ambition, publicly laying down her priesthood, and in 2008, in solidarity with its women, joining the Roman Catholic church. It was not a theological conversion, but, after long reflection, a spiritual impulse to join the disempowered. She did not renounce her past, and continued to worship in both churches. For Una, the barriers of church history had evaporated.

She was born in London into a cosmopolitan family. Her father, George Hill, from a family of timber merchants in the then Russian Baltic, was a British spy in both world wars, finally with the rank of brigadier. He left her mother, Hilda (nee Pediani), before Una was two. Una recounted that she spent her childhood being looked after by her mother’s family and friends in France, Latvia, Italy and Britain, and speaking Russian and French as well as English.

At the start of the second world war, she was in Hampstead, north London, living in the Russian émigré community. The war left a deep mark. Three of her cousins were Baltic Germans fighting on Hitler’s side in Russia. Two of them were killed, the third was one of Stalin’s prisoners for 12 years.

Una was sent to St Paul’s girls’ school, and to Malvern girls’ college, and at 19 went to study medicine at Girton College, Cambridge. There, her nominal Christianity turned into Christian activism. “The war and living among refugees influenced me to become a doctor and a socialist,” she later wrote to me in a letter. “Love your enemy and peace with justice became the crucial driving forces of my life.” Surrender of personal ambition led the young doctor to join the Community of the Holy Name, an Anglican religious order, in 1954.

The community sent her to a hospital in Liberia, west Africa, but within three years her vow of obedience collided with her convictions. In 1957 she became ill and a monk from an American order also working in Liberia offered to take her back to Britain. In a matter-of-fact way she recounted: “When we got to Paris we decided to get married. It was not so much a love affair as simply the right thing to do.” Leo Kroll, many years her senior, was in consequence out of work as a priest. Una and Leo had the first of their four children a year later and in 1959 set off to work in what is now Namibia. They hated the racist laws, became involved with the anti-apartheid struggle and within two years were expelled from the country.

In 1961 Una, with Leo in support, took up life as a GP on a large housing estate in St Paul’s Cray, south-east London. She was to combine that with many years of campaigning for women’s rights, spurred on by the injustices she experienced in her daily work. Sexism in the church made her blood boil.

She became an honorary deaconess in 1970 in the south London parish of another iconoclast, the Rev Donald Reeves – “that dangerous man”, as Margaret Thatcher called him. Rebels do not always hit it off. These two did. However, Una was not a natural team player. Successive curates found their colleague hard to take. In the general election of October 1974 Una stood as an independent candidate in the Sutton constituency in support of equal opportunities. It gave her a platform and a little more than 300 votes.

With an ever stronger inner call to the priesthood, she turned her fire on the church. It was to be a long struggle, but the tide was slowly turning. Some members of the Movement for the Ordination of Women were ill at ease with her militant style. Her opponents both feared and admired her. But it was the institution, not people, with whom she was spiritually at war.

Eventually, the radical campaigner began to give way more and more to the gentle and patient listener, wise counsellor, soul friend to many and spiritual director both of men and women. In this capacity she helped my wife and me to weather the traumas and ultimate death of a disturbed child. The BBC invited her to join a team responding publicly to people’s problems.

Widowed and retiring from medicine in 1987, she moved to a cottage beside a parish church in Wales, living as a contemplative nun. “No amount of good works,” she wrote at that time, “has been sufficient to halt our lemming-like rush towards the precipice of destruction. If there is to be justice in the world it can only come about by repentance on a large scale.” To be nearer her children, she moved in 2003 to a small flat in Bury, Greater Manchester.

Una’s life was a passionate, stormy love affair with the church. In her final years, physically frail but still mentally and spiritually vigorous, she embraced a solitary life of prayer for the many she loved and for the peace of the world. The storm had abated, though not all of her righteous anger. To the last, compassion remained.

She is survived by her children, Florence, Leo, Elizabeth and Una, and 10 grandchildren.

• Una Margaret Patricia Kroll, doctor, priest and campaigner, born 15 December 1925; died 6 January 2017