A report published by the University of Plymouth and Bournemouth University concludes:

Research has revealed that nearly 67% of all tweeting MPs belong to Labour ahead of 18% for the Liberal Democrats, with the Tories relegated into third place with just 12%. When you factor in the proportion of MPs that each party boasts, it is clear that the Lib Dems are leading the way when it comes to embracing the popular social media site.

And yet overall, just 51 of our 645 MPs are classed as regular Twitter users…

MPs tend to use Twitter as a means of promoting their activities in their constituency or when they are in Westminster, and again, the research has identified several trends:

1. On average 27% of MPs tweet as part of an impression management strategy. MPs promote their activities, such as giving speeches, speaking in parliament, holding positions or launching a policy document to help build a positive impression of them both as a professional and as an individual.
2. 21% of MPs’ tweets are used as promotion of self whereby the MP seeks to present a ‘hinterland’ which shows them as human beings. This tends to include details of their personal life, personal interests, such as sport and music and the use of humour.
3. 14% of MPs’ tweets support their constituency service role where they explain what they are doing in the constituency, highlight local issues and mention local constituents.
4. Only 11% of MPs’ tweets are partisan in nature. So this means that MPs are far more likely to raise their own profile rather than that of their party!

You can read more here.