ITV said it has taken "appropriate disciplinary action" over the incident where This Morning presenter Phillip Schofield confronted David Cameron with a list of alleged paedophiles.
Schofield was roundly criticised earlier this month after he handed the Prime Minister a list of names - understood to be Conservative Party figures - during the live show which he said he had put together from internet rumours.
An ITV spokesman said: "Last Thursday we began an investigation into the circumstances surrounding the mistake on that day's This Morning programme, for which both Phillip Schofield and ITV apologised.
"This investigation has now concluded and the appropriate disciplinary action has been taken.
"We sincerely apologise because the way in which the issue was raised was clearly wrong and should have been handled differently. We have taken steps to make sure our editorial processes are always properly followed, which was not the case in this instance, and to ensure such an error will not be made again."
TV regulator Ofcom has received around 100 complaints about the incident and is considering whether to launch an investigation.
The presenter was later forced to apologise after the list was briefly exposed on screen.
After being handed the list, which Schofield assembled after trawling the internet for three minutes, the Prime Minister warned that online discussions of an alleged paedophile ring could degenerate into a "witch-hunt" against people who are gay.
Politicians lined up to criticise Schofield, with policing and criminal justice minister Damian Green describing his actions as "tasteless and silly". Shadow home secretary Yvette Cooper warned against the danger of an investigation "driven by internet frenzies" and Tory MP Stuart Andrew denounced the presenter's ambush as "completely irresponsible and an outrageous stunt".
ITV apologised on the next day's show and emphasised it was not pointing the finger at anyone in particular.