ITV presenter Phillip Schofield has come under fire after handing the prime minister a list of alleged paedophiles during a live TV interview.
Downing Street said the ambush was "irresponsible" and a "silly stunt" after David Cameron warned that such actions could result in a witch hunt against gay people.
Although Schofield was clearly attempting to keep the card turned away from the cameras and the names were only visible for a fraction of a second, it is possible that the identities of individuals may have been disclosed, potentially leaving ITV exposed to legal action.
The presenter has since apologised for flashing the names, saying "there may have been a misjudged camera angle for a split second."
A Downing Street source said: "This silly stunt has resulted in people's names being put out there. They will want to vigorously defend themselves.
"The prime minister has taken necessary serious action on child abuse allegations. He is also concerned about a separate issue where people are facing an internet witch hunt. It's important allegations are handled properly - and people's reputations are not unnecessarily smeared."
Conservative MP Stuart Andrew, who was a councillor in Wrexham at the time of the original inquiry into the North Wales abuse scandal, criticised Schofield saying it was "a cheap shot".
Mr Andrew said: "Given the serious nature of this whole situation and the real complexity in terms of making sure these victims have the confidence to come forward, I thought it was a very cheap stunt to hand a list to the PM on a TV programme. It is not acceptable to take a cheap shot on something that is so fiercely sensitive.
"Anybody who has got any allegations to make must make them to the police, so they can be properly investigated."
Cameron, who was unprepared for the question and did not look at the list, replied: "I am worried this could turn into a witch hunt against people who are gay.
"I've heard all sorts of names being bandied around and what then tends to happen is that everyone sits around and speculates about people some of who are alive and some of who are dead," he said.
"I do think its very important that anyone who's got any information about any paedophile no matter how high up in the country or whether alive or dead go to the police. This is very important."
He added: ""There is a danger if we are not careful that this can turn into a sort of witch hunt, particularly about people who are gay, and I'm worried about the sort of thing you are doing right now, taking a list of names off the internet."
Cameron ruled out holding a "mega inquiry" into abuse rather than multiple investigations.
"I think the real question is, would that help us get to the truth any quicker. I'm very anxious that the BBC finds out what went wrong that allowed Jimmy Savile to do all those things over so many years," he said.
"I think the fastest way of that happening is with the former judge that they've got doing that investigation.
"I want to find out what happened in north Wales. The fastest way of finding out is with the judge that I've appointed.
"The idea that if you had one mega inquiry that you'd speed everything up, I'm not sure this is true.
"I don't rule out taking further steps. I want the government to be absolutely on top of this, I don't want anything to be covered up. If there are more things we have to do, we will do them."
Schofield has also come under fire under Twitter, where is known as @schofe and has nearly two million followers.
Schofield has since apologised for accidentally flashing the card to the camera, saying: “If any viewer was able to identify anyone listed, I would like to apologise and stress that was never my intention. I was not accusing anyone.
“Unfortunately there may have been a misjudged camera angle for a split second as I showed the prime minister some information I had obtained from the internet. I asked for his reaction to give him the opportunity to make a point, which he very clearly made on the dangers of a witch-hunt.”
Mr Cameron's official spokesman warned that "naming names could have implications for future criminal prosecutions".
The spokesman told a regular Westminster media briefing: "These issues need to be looked at properly and people shouldn't throw accusations around and smear people. If they have got allegations, if they have evidence, they should hand it to the police.
"We should not have people throwing names around, throwing allegations around and trial by Twitter.
"There are lots of accusations flying round and many accusations on the internet. We need to be very careful."
The government has ordered an inquiry into allegations that a senior Thatcher-era Tory political figure sexually abused children, and that it was covered up.
The move came after the BBC's Newsnight programme broadcast allegations that the man was part of a paedophile ring that abused boys from the Bryn Estyn care home in North Wales during the 1970s.