The report from the BBC Trust's Editorial and Standards Committee said the failure by Newsnight was "extremely concerning".
It found that the freelance reporter Angus Stickler, who brought the story to Newsnight, was considered a "safe pair of hands" and may have been subjected to "lighter-touch editorial checks" than if he had been less well-known to the BBC.
It said the report was wrongly treated as if it had two sources, Steve Messham, and an interview with a second victim broadcast on BBC Five Live in 2000, who could not be contacted during the making of Newsnight.
The Trustees agreed that members of the Newsnight team were wrong to regard this as a report with two sources, given that the second witness could not be found.
The Trustees found it particularly concerning that, at no point in advance of the broadcast of the Newsnight report, was Mr Messham shown a photograph of Lord McAlpine and asked to confirm that he was the individual at the centre of the allegations.
The BBC Trust has said that the airing of a Newsnight report which led to Lord McAlpine being wrongly named as a paedophile resulted largely from a failure by members of the team to follow the BBC's own editorial guidelines.
The broadcast on 2nd November was a "grave breach which had been costly to all concerned" and resulted in the public being misled, the Trust's Editorial Standards Committee (ESC) found
And in its findings, the committee ordered another report by the BBC next year into what steps will be taken to make sure the corporation "learns from these events".
Newsnight editor Peter Rippon decided to drop the programme's Jimmy Savile investigation and later wrote a blog about the decision, which contained several factual inaccuracies.
He "stepped aside" from his role while the review was completed.
BBC director of news Helen Boaden and her deputy, Stephen Mitchell, both were also described by the corporation as having willingly "stepped aside" until the end of the inquiry.
But they apparently challenged that description, with their lawyers notifying acting-DG Tim Davie they felt capable of carrying on in their roles during the investigation.
Boaden and Mitchell were accused of pulling back from decisions relating to child abuse or Jimmy Savile. A BBC statement said they had been temporarily removed after creating a "lack of clarity" within its editorial "chain of command".
BBC Trust chairman Lord Patten and the corporation's acting director general Tim Davie will give a press conference shortly after midday to follow the publishing of the Pollard Report into Newsnight's decision to drop its Jimmy Savile investigation.
Patten and Davie are expected to outline whether disciplinary action will be taken against staff, including Newsnight editor Peter Rippon, BBC director of news Helen Boaden and her deputy, Stephen Mitchell.
The publication of today's review will coincide with a separate report into how Newsnight reported an incorrect story which implicated Lord McAlpine in child abuse allegations.
Witnesses who gave evidence included BBC executives and Newsnight journalists, some under questioning from a QC, to establish why a planned news report on Jimmy Savile did not go ahead. Those questioned are thought to include:
- Director of news Helen Boaden
- Newsnight editor Peter Rippon
- Former Director-General Mark Thompson
The review was is carried out by former Sky News executive Nick Pollard.
A review which looked into why Newsnight axed a report into Jimmy Savile's decades of sexual abuse will be released today.
The BBC denied claims it dropped the show because it clashed with tributes to the DJ who died in 2011.
Lord McAlpine's lawyer told ITV News that now libel settlements have been agreed with BBC and ITV they will move to deal with 20 "high-profile tweeters".
Though solicitor Andrew Reid decline to name those Twitter users, he did said they would asked to pay damages in the thousands.
Asked about why the ITV settlement was lower than the BBC's, he said it was a "sensible settlement" and they had accepted ITV's position that "the fire was well lit" by Newsnight and Philip Schofield's actions "really just added oil to the flames".
Mr Reid also confirmed he spoke to Scotland Yard about those Twitter users who "maliciously" retweeted the Conservative peer's name in relation to the claims, which he described as "a criminal offence".
Lord McAlpine has asked those who wrongly accused him to apologise formally and pay a "sensible and modest amount", which he plans to donate to the BBC's Children In Need appeal.
Mr Reid added, "I think the Government having seen this will need, possibly, to have a clear piece of legislation to make sure that Twitter can't be used to bully".
Commenting on the settlement reached with ITV and Phillip Schofield, Lord Mcalpine said: "I am pleased to have reached a pragmatic settlement".