EastEnders actor Steve McFadden said phone hacking ruined his relationship with his ex-girlfriend and co-star Lucy Benjamin.
The actor, who plays Phil Mitchell in the much-loved soap opera, told London's High Court he became increasingly suspicious of his former partner, believing she was "shouting her mouth off" to the press when it was Mirror journalists stealing information from the couple's phones instead.
The 55-year-old actor became so perturbed by what he thought were her sly actions that it put him off from proposing to her. "The biggest factor that stopped me was thinking that Lucy had a big mouth and was giving out information," he told the court.
"All the articles in the Mirror's newspapers that were constantly being published about us made me suspect Lucy. I thought she was shouting her mouth off. Now of course I know it was nothing like this and it was the Mirror's journalists stealing information from our phones."
He added: "I now know that messages I left for Lucy must have been heard by MGN's journalists. Although I find this appalling, in some senses, I am relieved to finally know why and how so much information came out about me and Lucy.
"The sad thing is that you can't turn back the clock on what I thought and accused Lucy of at the time, which was that she was betraying me."
He said the articles printed also had a detrimental impact on her career, one in particular left her "sobbing inconsolably in the foetal position" in 2002.
He said she believed they were responsible "for putting her out of work and making her unemployable, and I think she was right".
Fellow EastEnders stars Shane Richie and Jessie Wallace did not speak to each for five years after suspicions were raised when the tabloid printed stories about them. Emotionally distraught, Richie recalled how someone on the set warned people to not tell "anything to Shane Richie because he's 'gobby', he talks to the press".
Mirror Group Newspapers (MGN) admitted the actor appeared in 12 stories it published between 2003 and 2005.
Lauren Alcorn, ex-girlfriend of footballer, Rio Ferdinand, also expressed her disgust at appearing in three articles, from 2002 to 2006, as a result of phone hacking at the Mirror.
The cases of actress Sadie Frost, ex-footballer Paul Gascoigne and TV producer Robert Ashworth, former husband of ex-Coronation Street actress Tracy Shaw are also due to be heard during the hearing.