The bisexual deputy-leader of the Liberal Democrats, Simon Hughes, is to sue News International over the hacking of his phone by a private investigator working for the now defunct News of the World.

Glenn Mulcaire, the private investigator hired by the paper has already pleaded guilty to hacking into Hughes’s messages, along with seven other people’s voicemails in 2006.

“It is important now that all those who were clearly the subject of criminal activity help to get to the bottom of what happened during this dark period in British journalism,” Mr Hughes told the Evening Standard.

“I have always been clear that the reason why I was most critical about illegal activity in my case was not the effect on my reputation but the invasion of privacy of others – constituents, colleagues, family and friends who should never expect to be the subject of illegal press intrusion.”

Mr Hughes was forced to come out as bisexual by the News of the World’s sister newspaper The Sun in 2005, in an interview to respond to claims to be made by the newspaper that he had contacted men using a gay telephone chat service.

Because Muclaire has already admitted to hacking Mr Hughes’s voicemail, he will be unable to resist any court order requiring for him to disclose who asked him to intercept Mr Hughes’s messages.