They send messages about cats, squidgy cake and Take That. And sometimes about politics.
MPs are spending almost 1,000 hours a year on Twitter, the social networking site, according to research.
The number of MPs tweeting - sending messages of 140 characters or fewer - has more than doubled from 111 in January last year to 275 today, and is expected to go on rising as more politicians sign up.
Keen tweeters include Nick Clegg, the Deputy Prime Minister and Ed Miliband, the Labour leader.
But David Cameron, the Prime Minister is famously anti-Twitter, after provoking controversy in 2009 when he said during a radio interview: "The trouble with Twitter, the instantness of it - too many twits might make a ----."
The Tories have the highest number, but the lowest proportion - of MPs on Twitter - 110 out of 305, or 36 per cent.
The Lib Dems, by contrast, have the lowest number but the highest proportion of MPs on the site, with 57 out of 100, or 57 per cent. Labour has 122 out of its 255 members tweeting, 47 per cent.
Charles Kennedy, former Lib Dem leader, who has posted just eight updates this year, is a "lurker", while the "obsessives" include Gavin Shuker, the Labour MP for Luton South, who posted 17 times in one day last month.
On his Twitter profile Mr Shuker describes himself as a "shadow environment minister, though more likely to tweet about kittens".
Kevin Brennan, Labour MP for Cardiff West, tweeted about guitar jamming, while Cheryl Gillan, the Conservative MP for Chesham and Amersham, posted a message saying: "Cardiff thobbing with Take That fans. feel undersdressed no stetson."
Liz Kendall, the Labour MP for Leicester West, tells her 3,700 followers: "Squidgy cake. In my humble opinion, best cake in world."
The researchers found that in a single week when Parliament was sitting during June MPs sent almost 2,500 messages on Twitter, equivalent to 118,000 messages over the course of a (48-week) year.
With each tweet assumed to take 30 seconds to compose, the researchers concluded that MPs are spending almost 1,000 hours a year posting updates.
Jo Swinson, the Lib-Dem MP for East Dunbartonshire said she used Twitter "to promote local causes and groups", but added: "It's not going to stop me knocking on doors to speak to people."
Olly Kendall director of westminsterpa.com, said MPs were using Twitter to "reveal a more personal side to their followers" rather than simply to "parrot political messages".
The site allowed them to reach constituents and the media "without spending hours writing press releases or blogs," he said.
Voters can also check how hard their MPs are working by looking at their Twitter feeds to see whether they are attending events in their constituency, he said.
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