During the second world war, working for the Special Operations Executive in France, Rose Robertson, who has died aged 94, was billeted with two young male French resistance agents. One night she entered their room and found them in an embrace. There was mutual embarrassment. Rose knew nothing about homosexuality and was curious. Eventually she plucked up the courage to ask. Both men told stories of family prejudice and rejection. Their story affected her deeply.

But it was not until the 1960s that she decided to do something about it. In 1965 she took in two young male lodgers and quickly realised that they were lovers. Hearing that they, too, had suffered because of their parents' attitudes, Rose was prompted to set up Parents Enquiry, Britain's first helpline to advise and support parents and their lesbian, gay and bisexual children, which she ran from her home in Catford, south-east London, for three decades.

Rose was soon flooded with phone calls and letters, at a rate of around 100 a week. These came from distressed gay teens and from parents who were variously bewildered, distraught, angry, guilty, ashamed and hostile towards their children's homosexuality. Often she mediated between parents and their offspring, nearly always successfully. Occasionally, she was verbally abused or physically attacked by irate parents. She was also targeted by homophobes, with arson attacks on her home, excrement dumped on her doorstep and abusive phone calls and hate mail.

From the mid-70s onwards, a growing number of referrals came from the police and social services. Authorities which had been wary of supporting criminalised gay teenagers (the age of gay consent was equalised at 16 only in 2001), were impressed by Rose's family-oriented approach. She won public support from the agony aunts Marjorie Proops and Claire Rayner. She was a frequent speaker at universities, churches and medical seminars, and was a regular on TV and radio throughout the 1970s and 80s.

Rose grew up in Deptford, south-east London, daughter of Arthur Laimbeer, a merchant seaman who was absent for much of her childhood, and his wife, Rose. Unhappy at home and keen to escape, she twice during her teens ran away from home to join troupes of travelling actors. She eventually settled into a series of secretarial jobs, most notably with a travel agency in Mayfair.

The war transformed her routine existence. Rose was always reluctant to speak about her role with the SOE, partly out of modesty, partly due to trauma and partly because of what she described as a "sort of brainwashing we were subjected to during training, in order that we would not break under Nazi interrogation".

According to what she told me, she joined the SOE in 1941 and was parachuted into occupied France. She spied on German troop deployments and acted as a courier, liaising between the resistance and allied military HQ in Britain. When her network was betrayed, she escaped. But others were captured. I was not able to corroborate Rose's role independently because many SOE records were destroyed or lost. However, I am inclined to believe her.

After the war, Rose returned to secretarial work for an industrial clothing factory. She married George Robertson, a retired music-hall artist, in 1954, and devoted the next decade to her job and bringing up their sons, Paul and Chris.

During her work with Parents Enquiry, Rose discovered a natural flair for therapy and soon extended her counselling to all aspects of sexuality and to a wide range of mental and emotional issues. She refused payment, financing her work from her salary and later out of her pension, and continued working until shortly before her death.

Although Parents Enquiry has now closed, the work Rose began continues through organisations such as Friends and Families of Lesbians and Gays and Parents, Families and Friends of Lesbians and Gays.

George died in 1984. Rose is survived by her sons; her grandchildren, Claire, Emma and Matthew; and two great-grandchildren.

• Rose Ellen Robertson, SOE agent, therapist and counsellor, born 28 October 1916; died 10 August 2011