Twitter appears to be the embodiment of youth culture with tech-savvy and fast-thumbed teens firing off short updates filled with abbreviations about their lives. But it turns out that the keenest users are the greying brigades of the middle-aged.

More mature users, led by famous tweeters such as Stephen Fry, Jonathan Ross and Sarah Brown, are the driving force behind the popularity of the site. New research shows that 45 54-year-olds are 36 per cent more likely than the average to visit the site, with figures from comScore, the internet market researchers, showing that the majority of the 10 million Twitter users worldwide are aged 35 or older.

Twitter is a social networking and “microblogging” site, where users post short updates — “tweets” — of up to 140 characters via the website or a mobile phone. More than 3.5 million people signed up in the first two months of this year.

Celebrities such as Russell Brand and Jamie Oliver are avid users, while Barack Obama used it as a tool during last year’s US presidential elections to talk directly and quickly to hundreds of thousands of followers.

Stephen Fry, 51, the actor and comedian whose tweets are followed by about 400,000 people, has become a leading advocate for the service. “I love how Twitter confirms my all too often assaulted belief that most humans are kind, curious, knowledgeable, tolerant and funny,” he wrote on his blog.

Celebrity tweeters have pushed others towards the site. “It’s the role model thing,” said Richard Drake, 51, from London. “You see Stephen Fry and think, they’re doing it, so why can’t you? You’re not teenagers, so you’re no longer following the crowd to the same degree perhaps.

“But you think, well, he’s finding it interesting, there’s something happening there, and people my age are doing it.”

Other social networking websites, such as Facebook and MySpace, have also seen an increase in the number of older people signing up in recent months. But the simplicity of Twitter has made it most popular with the golden oldies and 20 per cent of all tweeters in Britain are over the age of 55, compared with 12 per cent of Facebook users.

However, it seems that the young are being put off by the increasing number of older users. “I do think there’s a feeling that, if your parents are doing it, suddenly it’s not cool any more,” said Jamie Gavin, an analyst at comScore.

Ageing tweeters also said that whereas Facebook seemed to reveal every aspect of your life — something the young seem more at ease at doing — Twitter was less intrusive, and often is used by people at work.

“I only Twitter professionally,” said Ian Williams, 41, an executive at a price comparison website. “For us, its just another communications tool. That’s the beauty of Twitter. If you decide something is not interesting or inane, you can stop following it. It's just not invasive.”