Danny Jarvis is a football coach with a degree in leisure management. He is funny, has an independent mind and loves his job. He also suffers from cerebral palsy and relies on a full-time carer to wash and feed him. At 32 he was still a virgin until his friend, Jennie Williams, took him to a brothel in Amsterdam.

For Jarvis it was a sexual awakening; for Williams, it was a wake-up call. Speaking to Jarvis after his first sexual experience, he told her he was worried it had gone badly because he didn't climax immediately. This surprised Williams, who is also managing director of the disability charity Enhance the UK. "In every other way, Danny is sociable and knowledgeable," she says. "But when it came to sex he didn't know anything because he'd never experienced it and no one had ever told him about it."

Williams began researching sex and relationships education (SRE) for disabled people. She found that very little was available. Despite recent TV programmes and films such as Sex on Wheels and The Sessions having brought the sexuality of disabled people into the open, many are still being neglected when it comes to receiving a proper sex education. This has worrying implications for their safety, self-esteem and sexual health.

According to a 2010 report by the disability charity Leonard Cheshire, almost 50% of disabled people surveyed said that they received no SRE at school. At the same time, people with severe physical disabilities are not exposed to the same everyday situations in which other young people learn about sex. They often also lack the ability and privacy to experiment with their own bodies.

Jarvis's condition means that he occasionally ejaculates involuntarily. The first time this happened, he had no idea what was going on, simply because no one had taken the time to explain sex to him. His mother found it difficult to discuss the subject and it was not addressed at his school, either. This began to have a serious impact on Jarvis's self-esteem. "At school I was under the impression that no one would want to have sex with someone in a wheelchair," he says. By the time he was in his 20s he decided to take counselling.

People with disabilities – especially those requiring round-the-clock care – can often feel desexualised, Williams says. "If you have to have your bottom and face wiped for you, these are things that are associated with being a child. It is then assumed that you do not have adult sexual needs and, in the eyes of others, you become completely asexual, even if you're not."

Teresa Doyle, from the sex education charity Brook, agrees. She says that schools and parents often display "an utter blindness" to the sexual needs of disabled pupils.

In one instance, Doyle was called to a school to help a girl with a learning disability who required a pregnancy test. The girl's teachers were convinced that she was lying because they did not believe that someone like her would be sexually active. The girl's pregnancy test proved positive. Doyle explains that the girl had "ended up having sex because she didn't know what it was".

Doyle's experience shows that SRE is vital for people with learning disabilities. A 2008 paper on teenage pregnancy in Wolverhampton states that around 28% of teenage mothers have some form of learning disability. The paper also includes figures from a special school in the same area that 40% of its female pupils had become teenage mothers within 18 months of leaving. Meanwhile, research in the Netherlands has shown that men with a learning disability are eight times more likely to contract sexually transmitted infections than those without.

In the UK, Ruth Garbutt – a research fellow at Leeds University's centre for disability studies – has produced the report Talking About Sex and Relationships: The Views of Young People with Learning Disabilities. It shows that sex education provision for people living with disabilities is inconsistent, both at mainstream and special schools – and that teenagers are left vulnerable because of these shortcomings.

One parent told Garbutt that her son had pulled out all his pubic hair because he was ashamed of it. Another reported that their son was caught having sex with men in public toilets. "If he'd known more about what was safe and unsafe, and what was public and private then he might not have got into that situation," Garbutt says.

Garbutt also heard that some doctors and teachers were advising parents not to talk about sex to their disabled children. Williams believes this sweep-it-under-the-carpet approach must change. "The truth is that disabled people have sex and disabled people like sex. But they don't have access to the same advice and support as their peers."

In an attempt to provide that support, Enhance the UK has launched the Undressing Disability campaign, which aims to create a comprehensive model of SRE for disabled people.

For Jarvis the message is simple. "I think if someone had talked to me about sex before, I wouldn't have been so hung up about it," he says. "In school they should tell people that just because you have a disability, it doesn't mean you can't fall in love, have kids and be happy."