George Entwistle announces his resignation as BBC director general. Picture: Jonathan Brady/PA Wire

BBC director general George Entwistle tonight quit over the “unacceptable” Newsnight broadcast which wrongly implicated a senior former Conservative in a child abuse scandal.

Earlier Mr Entwistle said the report, which falsely implicated the former senior Tory Lord McAlpine should never have been broadcast.

During an interview with the Radio 4 Today programme he disclosed that he had not known in advance that the report, shown on November 2, was going out.

His disclosure led some MPs to question whether he was the right person to lead the BBC.

In a brief statement outside Broadcasting House this evening, Mr Entwistle said that he had decided to do the “honourable thing” and step down from his post.

He said: “When appointed to the role, with 23 years’ experience as a producer and leader at the BBC, I was confident the trustees had chosen the best candidate for the post, and the right person to tackle the challenges and opportunities ahead.

“However the wholly exceptional events of the past few weeks have led me to conclude that the BBC should appoint a new leader.”

Standing alongside him, the chairman of the BBC Trust, Lord Patten said it was “one of the saddest evenings of my public life”.

“At the heart of the BBC is its role as a trusted global news organisation,” he said.

“As the editor in chief of that news organisation George has very honourably offered us his resignation because of the unacceptable mistakes - the unacceptable shoddy journalism - which has caused us so much controversy.

“He has behaved as editor with huge honour and courage and would that the rest of the world always behaved the same.”