London (CNN) -- Singer Charlotte Church on Monday blasted the News of the World tabloid for its decision to publish a lurid story about her father having an affair while her mother was getting treatment for mental illness.
"They knew how vulnerable she was and still printed a story like that, which is just horrific," she said.
The former child star also spoke of her anger at finding out her phone may have been hacked by a private investigator working for the Rupert Murdoch tabloid.
The investigator, Glenn Mulcaire, had details of her phone and those of her parents, friends and former boyfriends, Church said police had told her.
She was testifying before a wide-ranging British government-backed inquiry into press ethics and practices in the country.
Sparked by the revelation that News of the World tabloid hacked into the voice mail of a murdered 13-year-old girl in search of stories, the Leveson Inquiry has been hearing from high-profile figures for more than a week.
Church described how upset she was at the leak of the news of her daughter's birth, the rifts it caused with her family and friends when she accused them of revealing the details, and her later guilt at realizing the source was probably hacking, not leaks from those close to her.
And she said falsehoods published in the press were particularly damaging because readers believe there are rules to prevent that from happening, "So if they see it in print, it must be true -- and that's not the case."
Former Tony Blair spokesman Alastair Campbell is due to testify later this week, but a written copy of his opening statement appears to have leaked online.
Paul Staines, who blogs as Guido Fawkes, posted what he said was a copy of Campbell's testimony in which he speculates about the possibility that the Daily Mirror found out though phone hacking that Tony Blair's wife was pregnant.
"I think it is at least possible that this is how the stories got out," Campbell says in the statement published by Staines.
Campbell said on Twitter Sunday he was "genuinely shocked someone has seen fit to leak my statement to Leveson."
The Daily Mirror is not a Murdoch paper. Piers Morgan was editor of the paper at the time of Cherie Blair's pregnancy, and he now hosts the show "Piers Morgan Tonight" on CNN.
Morgan, who has vigorously denied ordering phone hacking, is due to testify before the Leveson Inquiry at a later date yet to be determined.
Celebrities who have already testified before the inquiry include "Harry Potter" author J.K. Rowling and "G.I. Joe" actress Sienna Miller, who both complained of being hounded by paparazzi.
Actor Hugh Grant also appeared before the panel, and he implied that police leaked information to the tabloid press. He also accused the Mail on Sunday of hacking.
Police investigating phone hacking by journalists say that about 5,800 people, including celebrities, crime victims, politicians and members of the royal family, were targets of the practice by journalists in search of stories.
It involves illegally eavesdropping on voice mail by entering a PIN to access messages remotely.