On Tuesday I was at a breakfast event with Tweetminster, the guys who tell you all you need to know about politicians tweeting. As it drew to a close I succumbed to the urge to check my Twitter feed, only to find a series of bizarre, seemingly random-generated questions. My first thought was that I'd forgotten an impending 'twitterview', which people were hijacking by sending in silly questions. But then I sussed out that the 30,000 followers of the comedian Ross Noble had been given orders to bombard me with tweets.

Is there any point to all of this? Well, it was fun – and that's why I responded. If you ask most politicians why they tweet they'll say it's because they enjoy it, rather than because of any cost-benefit-analysis they've done in terms of time, aggro and political capital.

But there's a political pay-off too. I got a lot of replies on Twitter along the lines of 'MPs are human after all!' and 'I think @KerryMP has swung me towards Labour'. Yesterday many of the 600+ new followers I acquired courtesy of Mr Noble were following MPs tweeting through Prime Minister's Questions and the Pre-Budget Report. People have even joined Labour after talking to MPs on Twitter, and turned out to campaign for them too.

And that's because Twitter, when used to engage and not simply to broadcast, reveals the person behind the politician; their principles, their passions, their personality. It's the authentic voice that comes through, of the MP and in aggregate, of the Party. People appreciate that.

Another impact of Twitter is to turn armchair politicians, who in the past would have sat ranting at their television set, into active participants in political debate. (See #bbcqt, the tag for BBC's Question Time for one example, or #pmqs). And it's also bringing together people in the real world, whether it be at events like the Downing Tweet Christmas party organised by Sarah Brown (one million followers and rising), or "tweet-ups" at Labour Conference, or #pubqt where tweeters are now meeting in pubs to watch and tweet their way through Question Time.

It builds a sense of community, a sense of solidarity. Blogging, and commenting on blogs, often feels to me like a solitary activity; Twitter is like joining a lively group of friends in the pub. Some of you are arguing, some are being serious, some are being silly.

So Twitter will be a force in persuading more people to take an interest in the coming General Election. It will also accelerate the speed at which stories are broken, dissected, rebutted, reframed during the campaign. No longer will Party HQ be able to plot things according to a daily grid. A speech given at midday and aimed at making the evening news could be a very different story once Twitter gets involved in scrutinising it. Take David Cameron's recent, poorly-researched attack at Prime Minister's Questions about funding for Islamic schools, or his health and safety speech: both torn apart on Twitter.

Twitter won't win the election for Labour, but if it convinces more people to take an interest in politics, and to get involved, and if it persuades some of them that politicians aren't the people they're often painted to be, then it's a very good thing indeed.

Kerry McCarthy is MP for Bristol East and Labour's 'Twitter tsar'