Simon Hughes, the deputy leader of the Liberal Democrats, has become the first Coalition MP to launch a damages claim against News International over phone hacking.
The London MP was one of eight victims, including members of the royal household and celebrities, who were named during the 2007 prosecution of private investigator Glenn Mulcaire, but Mr Hughes said he had decided to start proceedings this week to help "get to the bottom" of the scandal that led to the closure of the News of the World.
The senior Lib Dem gave an interview to The Sun in January 2006 while standing for his party's leadership, confirming that he had homosexual relationships after he was presented with what the newspaper described as "pretty incontrovertible" evidence that he used a gay chatline. There is no evidence the article was based on intercepted voicemails.
It is understood that Mr Hughes' claim relates to a period after the publication of that story between February and March 2006 when Mr Mulcaire, who was paid £105,000 a year by the NOTW for "research and information services", accessed his voicemails on eight occasions after obtaining the MP's PIN code.
In a statement, Mr Hughes, 60, said: "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.
"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."
The deputy to Nick Clegg is the eighth politician, including former deputy prime minister John Prescott and former Cabinet minister Tessa Jowell, to bring a lawsuit against News Group Newspapers, the parent company of the now defunct NOTW.
Mr Hughes, who is the first member of a Coalition to sue the NOTW for hacking at the time when it was being edited by former Downing Street communications chief Andy Coulson, joins a growing list of public figures seeking damages against Rupert Murdoch's British company, whose claims are likely to cost the magnate at least £20m.
Mr Hughes, who was the subject of a number of newspaper stories about his private life during his party's leadership contest in 2006, has played a prominent role in the hacking scandal, bringing judicial review proceedings against the Metropolitan Police along with Lord Prescott and former Scotland Yard senior officer Brian Paddick over the force's failure to uncover the full extent of illegal newsgathering. News International declined to comment on the case.