Do you see what I'm saying?

When Michael Bloomberg appeared during Hurricane Sandy last month, his sign language interpreter unwittingly stole his thunder. Lydia Callis translated the New York City mayor's announcements using every muscle she possessed. So expressive was she on a stage filled with stiff officials that CNN filmed a prime-time profile, Saturday Night Live sent her up in a sketch and websites around the world hummed with love for Lydia.

Translators should be invisible, but sign language interpreters must be seen to be heard. As Callis showed, this sometimes earns them an audience beyond the deaf community. It can be intentional. During the 2004 Presidential elections in Ukraine, Natalia Dmytruk tore up the script on state-run news to tell deaf viewers early results were "lies" and that "I am very ashamed to translate such lies to you". Her silent rebellion emboldened the protests that led to the Orange Revolution.

Such breakthroughs are rare, however. In the meantime, a dedicated profession works behind the scenes and from the corner of our television screens. Increasingly, the minority they serve, who can't hear but also struggle to be heard, say that government and media fail to give them access to society the rest of us take for granted.

Days after Sandy hits, Robert Skinner is working in a broom-cupboard BBC studio in west London. He's interpreting the previous night's edition of Question Time, which covered the US elections and the Newsnight crisis. Like Callis, he uses his whole body to convey meaning as well as tone. Later that night, deaf viewers will watch or record the programme with Skinner's signing laid on top.

British broadcasters are required by law to improve access for the estimated 10 million people in the UK who have some form of hearing loss. More than 800,000 of those people are severely or profoundly deaf. According to the charity Action on Hearing Loss, as many as 70,000 people use British Sign Language (BSL), many of whom cannot lip-read. Fewer than 1,000 registered interpreters help them to navigate life, be it via Question Time or, for example, during crucial medical consultations.

Skinner, who's 33 and refuses to cut his hair despite requests by his bosses (he describes his look as "curly-haired hippy") can hear but his parents and brother are deaf. BSL, which is recognised as an official language in Britain, is his first language. "When I got home from school on a Friday, my voice switched off and wouldn't turn on until Monday morning," he recalls. Opportunities for deaf people have improved since then. "When I was a kid they weren't doing the kind of work they do today," Skinner adds. "Now there are deaf company directors, doctors and PhD students."

Exclusion, however, remains a concern. Jeff McWhinney, who is deaf, is a leading campaigner and the former head of the British Deaf Association (BDA). In 2004, he launched SignVideo, a contact centre that uses interpreters to help deaf people make simple phone calls. Speaking on the phone via his webcam and Vicky, an interpreter who signs for him, McWhinney says deaf people in Britain watched Lydia Callis with envy.

"It was amazing to see an interpreter right next to the mayor," he says. "We saw the same with the President in the US elections. We don't have that here. During 7/7 for example, deaf people were getting visual images on the news but not important information. We're proud citizens but we're treated as lesser citizens."

Skinner, a freelance interpreter for Red Bee Media, which provides access services to the BBC, says an interpreter disappeared when President Obama made his victory speech this month. Similar omissions occurred during Jubilee and Olympic broadcasts.

Vicky Lamb, McWhinney's interpreter, says: "There should be a fundamental right to access information that affects your life, but also to choose what and what not to watch. Deaf people pay the licence fee. I can understand their deep frustration."

The BDA has complained to the BBC about the sidelining of sign language, which must be offered in 5 per cent of programming. A BBC spokesperson insists sign language is pushed off air only in exceptional circumstances and blames the Obama incident on operational problems. "We have apologised for the impact this had on viewers who rely on the signing service and remain committed to the role of signing on the channel," a statement adds.

Action on Hearing Loss (formerly known as the Royal National Institute for Deaf People) campaigns for better access beyond television. It called on the Government this year to set a minimum standard for communication for deaf people, and to improve the provision of interpreters. "There's still a huge way to go to ensure any kind of level playing field," says Helen Arber at the charity.

"BSL users suffer because they are few in number but have high support needs. That's the battle."

Last May, the charity also campaigned for healthcare providers to improve access and standards. Its survey revealed half of BSL users leave appointments feeling confused. "We're talking about vital information on medication or even traumatic diagnoses," Arber adds.

Back at the BBC, Clara Allardyce, Red Bee's signing manager, is one of a growing number of deaf interpreters Action on Hearing Loss is helping to train. She must sign while simultaneously watching a programme and reading subtitles. The BBC says 99 per cent of its broadcasts carry subtitles. Why do deaf viewers need sign language, which is more expensive to produce?

"My Mum is the perfect example of why," Allardyce says before she starts recording a children's programme. "She is deaf and doesn't have English language. A lot of deaf children are behind with their language because they don't pick it up like a hearing child would. For many users it's also the easiest way to communicate."

Words can be spelled out using the BSL alphabet, but images rather than "words" create a visual shorthand. They allow Skinner to interpret even the most fast-talking Question Time panellist. "Obama", for example, becomes the symbol for "O" followed by that for a flag. Expressive movement is essential to convey context or feeling. Many users also take great pleasure in studying and using BSL, which includes dialects and even accents. "When I watched Lydia I felt like I could see a Bronx accent," Skinner says. "It was like, 'yo, there's a stawm comin'. It was very cool."

Interpreters must also research programmes and keep up with the news to be sure of obscure phrases or words. Surprisingly, Skinner, who regularly interprets live news, says he finds fast-talking Question Time quite easy. "I can guess half the questions and even predict what MPs will say," he says. "But if I get Countryfile, say, then anything can happen."

Callis, meanwhile, says she was overwhelmed by the interest in her after Sandy but, she told CNN via her own interpreter: "If this is what's going to shine a light on the deaf community and the culture and language, then it's a beautiful thing."