Richard Wallace, editor of the Daily Mirror, said there is a possibility that phone hacking 'might well have been' going on without his knowledge
The editor of the Daily Mirror today expressed his "sincere regret" to Chris Jefferies, who was arrested as part of the Joanna Yeates murder investigation but later released without charge, adding that the case is "very much a black mark on my editing record".
In July last year Jefferies won "substantial damages" and an apology from eight national newspapers, including the Daily Mirror, in relation to their coverage of his arrest
Along with the Sun, the Daily Mirror was also found guilty of contempt of court, a ruling which the Mirror is now appealing.
Appearing before the Leveson inquiry today, Daily Mirror editor Richard Wallace said he was "not proud of what we did to Mr Jefferies", adding that he "made a very serious misjudgement".
When asked about the pressures of competition in this area, Wallace said "competition is always keen within Fleet Street".
"One always wants to beat competition but should not become reckless in seeking to beat the competition," he added.
He told the inquiry "Mr Jefferies' name will be imprinted on my brain forever more" and that the event "will change very much" the way he handles similar stories in the future.
"It is about creating a climate that makes all editors think perhaps longer than they have previously," he added.
Earlier in his evidence today Wallace was asked whether allegations made to the inquiry about phone hacking at the title were true.
In evidence to the inquiry in December former Mirror journalist James Hipwell claimed that hacking was "bog standard" at the newspaper.
"No, not to my knowledge," Wallace said. When asked whether there was a possibility it was going on but hidden from him he said: "It might well have been".
Trinity Mirror declined to comment, but has previously called allegations of phone hacking at the Sunday Mirror "totally unsubstantiated".
Wallace was also asked about his views on regulation, including how to approach this in a "digital world".
"There is already an opportunity here and we need to grasp it. Whatever this inquiry throws up as a new body, I believe there is a willingness in the digital world among internet news providers to themselves sign up to some kind of framework, because it gives them cachet."
He added that people are seeking "some kind of order" online, adding that "legitimate bloggers" and other online news providers "would welcome the opportunity to join".