George Entwistle has resigned as director general of the BBC. The news was announced by Entwistle and BBC Trust Chairman Lord Patten in a statement outside Broadcasting House on Saturday evening.
Entwistle said the "wholly exceptional" events of last week had convinced him to do the "honourable thing" and stand down.
"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," he said.
"However the wholly exceptional events of the past few weeks have led me to conclude that the BBC should appoint a new leader."
Entwistle and Lord Patten outside Broadcast House on Saturday evening
Lord Patten said the new acting director general would be Tim Davie, adding that Entwistle's resignation 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," said Patten.
"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."
Following news of the resignation, Culture Secretary Maria Miller said: "It is a regrettable but the right decision. It is vital that credibility and public trust in this important national institution is restored.
"It is now crucial that the BBC puts the systems in place to ensure it can make first class news and current affairs programmes."
Lord Patten said Entwistle had behaved as editor with huge honour and courage
The director general had faced an uncertain future after being engulfed by the latest scandal to blight the corporation's flagship Newsnight programme in which a Tory Peer was incorrectly implicated in allegation of child sex abuse.
Entwistle's resignation follows a day of heavy criticism which saw the director general mauled on the Radio 4's Today programme by John Humphreys, who probed the recently appointed editor-in-chief as to why he hadn't taken more of an interest into the programme's output, particularly in the wake of the Jimmy Savile scandal.
Entwistle told Humphreys: "In the light of what has happened here I wish this was referred to me, but it wasn't. I found out about the film the following day."
In a brutal examination of his boss's failings, Humphrey barked: "So there is no natural curiosity, you wait for somebody to come along to you and say 'Excuse me director general, but this is happening and you may be interested'?"
"You don't look for yourself, you don't do what everybody else in the country does, read newspapers, listen to everything that's going on and say 'What's happening here?'"
On Saturday evening, Labour deputy leader and shadow culture secretary Harriet Harman waded into the row, emphasising that something had gone "badly wrong" at Newsnight.
"The director general only took over the leadership of the BBC eight weeks ago, but he needs to show decisively that he is addressing the systemic problems which are in evidence here," she said.
Throughout the day, pundits and politicians lined up to point out the failings of the programme, its staff and the director general, including a broadside from parliamentary culture select committee chairman John Whittingdale, who slammed the BBC chief's "extraordinary lack of curiosity" in Newsnight's investigations.
During his savaging on the Today programme, Entwistle apologised for Newsnight's investigation leading to the incorrect "outing" of Lord McAlpine as the senior Tory paedophile, calling the reports "unacceptable", and announcing he would look into the affair and that he had "taken clear and decisive action to start to find out what happened and put things right".
LISTEN: Audio of Entwistle's Today appearance
Following the interview, former ITN editor-in-chief Stewart Purvis tweeted that the interview was the "most painful I've ever heard with a DG of the #bbc".
Purvis wasn't alone, with journalists, politicians and even current BBC employees criticising Entwistle's interview. The deputy national editor of the Guardian, Polly Curtis, said that: "I knew the film was being transmitted. Everyone on Twitter knew. How did George Entwistle not know?"
Former managing director of BBC Television Will Wyatt strongly criticised the entire affair, saying the fallout of the report was "a terrible blow to the reputation of the programme".
Speaking to the Guardian, Wyatt said: "I can't believe everyone on the payroll will be there in two months' time. This is not a time for sentimentality."
In an interview with the BBC, John Whittingdale, chair of the culture, media and sport select committee, criticised the BBC and ignorance of the Newsnight report, saying: "At the end of the day the editor in chief of the BBC, the director general, he should have satisfied himself that this programme was right to be broadcast and he wasn't even aware it was going out."
Whittingdale added: "You would have thought that whole of the BBC would be alert to make sure there weren't going to be any more blunders".
Meanwhile the BBC Trust has spoken out on the matter, calling the saga a "deeply troubling episode," and pressed Entwistle to "get to the bottom of this as a matter of the utmost urgency".
Twitter was alight with criticism and disbelief at Entwistle's interview, the most prominent of which you can see in our slideshow below: