The watchdog set up to regulate press standards has been branded "toothless" by MPs concerned it has never fined a newspaper.
Chairman of the Independent Press Standards Organisation (Ipso), Sir Alan Moses, strongly defended its record as he appeared before the Commons Culture, Media, and Sport Committee.
MPs questioned why Ipso, which was set up in the wake of the Leveson Inquiry in September 2014, had not fined any newspaper found to be in breach of standards rules, or demanded equal prominence for corrections of inaccurate headlines.
The committee also heard that a whistle-blower hotline set up for journalists to report breaches of the standards code had not resulted in any such incidents coming to light.
SNP MP and former journalist John Nicolson said Ipso was not able to deliver in key areas.
"I have a sense of slight gloom hanging over your evidence. Because, to summarise, you've said that you've issued no fines at all; almost no one is phoning your whistle-blower helpline; you've never made an order for equal prominence of headlines, regardless of the story since you were established - and all of this just creates a sense of slight toothlessness.
"You've given evidence that suggests you are not able to deliver in key areas, for whatever reason, not least that people don't often know who you are," the MP said.
Sir Alan insisted Ipso was doing its job as a watchdog.
"I do believe that we really do have teeth, in the sense that what we do, namely, the dictation to the newspapers when they are in breach of what they have to do about it in their newspaper, the words they have to use, for the first time, actually telling an editor 'you must put this in your newspaper in that space' is something that I think that they resist.
"We know that they resist it. They really dislike it. It really hurts them.
"I don't regard that as toothless at all, I regard that as really important," the Ipso chief said.
Labour MP Paul Farrelly asked why Ipso had not launched a probe into the case of Christopher Ware, who he said had been effectively falsely accused of murder in a press report.
Ipso chief executive Matt Tee told the committee that Mr Ware had taken separate legal action, adding: "Nobody approached us to ask us to do an investigation into it."
Sir Alan said he feared Ipso had caused "damage" when it did launch an investigation without receiving a complaint into the case of Brooks Newmark who resigned as a minister in 2011 after being accused of "sexting" an undercover reporter.
The Ipso head said: "That happened again right at the outset of when we were forming ourselves, recruiting staff, setting ourselves up, and we announced that we would investigate that ourselves, and we did investigate, and I fear that we may have done more damage than if we hadn't investigated."
Sir Alan, who insisted newspapers were now "chastened" because of the watchdog, said Ipso had issued 76 private advisory notices so far this year to prevent journalists "camping out" on people's doorsteps.
Pressed by Mr Nicolson on whether complainants who come to Ipso should trust, or not trust, the newspapers involved, the watchdog's Mr Tee said: "I'm saying 'don't not trust them'."