"It was pioneering," says Anne Weyman, the charity's chief executive.
"The women campaigning for this were acting against lots of criticism. Society was not very sympathetic. At the time those who had access to education and money could get contraception, but it wasn't available to the poor."
The campaign was finally won in 1974, when the NHS began offering free contraception to women for the first time. The agency's family planning clinics were brought under NHS control and this prompted a rethink. "We've really become a different organisation," admits Weyman. "It was a huge achievement to change from running a large number of clinics to being concerned with promoting sexual health education."
Today fpa concentrates on providing information on sex and relationships, along with campaigning for improvements in sexual health policies and training professionals to give good sex and relationships advice.
But while this work is popular - fpa's helpline receives about 100,000 calls every year - its advice leaflets for young people have faced the wrath of a sometimes hostile press.
"What's interesting is that when any of the newspapers want accurate information on sex and relations they come to us," says Weyman.
"We're a major source of information for the press and we do a lot of important work building links with the consumer magazines. The situation has changed and the criticism is focused on particular topic areas. At one time it was the very thought of providing contraception, but now it's providing contraception to young people and abortion."
But while the papers often disagree with fpa's work, Weyman finds the public is more open-minded.
"We've had people contact us about leaflets after reading the papers and when we give them a copy we get a very different response," she says.
While young people's access to information and advice about sex has never been better, there is a problem ahead. A legal challenge, due to be heard this year, will dispute the right of under-16s to access confidential advice on contraception and sexual health.
The challenge has been brought by concerned mother Susan Axon and, if successful, would mean professionals would have to inform parents if approached by a young person about sex-related issues. Weyman believes this would be a disaster.
"If Axon was to win it would have very negative consequences for young people," she says. "Without confidential advice, no-one would be willing to talk."
Weyman believes society has yet to tackle the mixed messages it gives out to young people. "We have sexualised imagery in papers, magazines, TV, adverts that give the message to young people that sex is exciting," she says. "But then we tell them we don't want to talk about it and worry that if we give them information they will rush out and have sex. It's completely illogical."
She adds that these mixed messages make policymakers nervous of increasing sex and relationships education. However, Weyman thinks the existing teenage pregnancy strategy is having a positive effect.
"Conception rates have been going down since 1998, although that isn't the case everywhere," she says. "It is important to have a long-term strategy on this because it is a very complex issue. It's an emphasis the Government needs to maintain."
- Anne Weyman became chief executive of fpa in 1996
- Before her appointment, she was director of information and public policy at the National Children's Bureau, where she worked for 10 years
- She originally trained as a chartered accountant but moved into the voluntary sector in 1977 after studying a degree in sociology