The BBC has spent around £5 million investigating the Jimmy Savile sex scandal so far and the final bill is still not in.
The corporation's annual report and accounts reveal that the Pollard Review, which looked at why the BBC dropped a Newsnight investigation into Savile, accounted for almost half of that.
It cost £2.4 million, before tax and VAT, which included £101,000 to cover the "legal and related costs" of Helen Boaden who was heavily criticised in the report.
The then Head of News was among senior executives criticised for failing to act while the BBC was plunged into chaos by the scandal.
The bill also includes £81,600 paid to former Sky News executive Nick Pollard for conducting the review and £893,501 paid to law firm Reed Smith, who advised on the process, as well as £107,000 paid to cover the legal costs of former director-general George Entwistle.
His immediate predecessor, Mark Thompson, was paid £86,000 for his legal and related costs.
Figures show the cost of the review and subsequent investigations into respect at work and the BBC's culture and practices while Savile worked there have cost £4.9 million excluding tax and VAT up to the end of March.
The third investigation, which will also examine the case of recently jailed Stuart Hall, will be published later this year sending the final bill even higher.
Writing in the report, BBC Trust chairman Lord Patten quoted Charles Dickens to compare the success of the Olympics coverage with the Savile scandal saying "It was the best of times, it was the worst of times".
He said the revelations about the scrapped Newsnight investigation and subsequent departure of Mr Entwistle were "low points".
He said: "The BBC seriously let down both itself and licence fee payers".
Matthew Sinclair, chief executive of the TaxPayers' Alliance, said: "Families up and down the country are having to pick up the cost of investigating this terrible scandal through their licence fees, which then reduces the resources available for making programmes.
"The bill for investigating the Savile case and its fall-out has been made all the greater by failings at the corporation.
"It is therefore vital, given its importance and the expense involved, that the Pollard Review is published in full rather than its current heavily redacted form.
"Senior BBC staff found responsible for serious failings must also be held to account for their actions rather than being let go with a secret pay-off, as has happened too often in the past."
Speaking to reporters after the publication of the accounts, new director-general Tony Hall said he wanted to change the culture at the BBC and called for "greater personal accountability" and a simpler corporation.
In a letter to Lord Patten, he said he had been "struck by the complexity of the organisation and inhibiting effect that has on creativity."
He added that he was "personally leading a major piece of work to look at how we can simplify our organisation".
Mr Hall said he hoped the BBC would be a "simpler" organisation by this time next year.
The accounts show the cost of the executive board rose from £2.5 million in 2011/12 to £4.1 million in 2012/13 with chief financial officer Zarin Patel's pay returning to £366,000 from £337,000 after a temporary move saw her give up a month's pay in March 2012..
The man behind the BBC's coverage of the 2012 Olympics, Roger Mosey, who is due to leave the BBC this year to become Master of Selwyn College at Cambridge University, has a pension pot of £2.8 million.
Ms Boaden's pension pot stands at £1.5 million, while Caroline Thomson, who had a total remuneration of £860,000 in 2012/13, has a pension pot worth £1.9 million.
Ms Thomson, who was regularly criticised for excessive expenses claims, was given £683,000 last year for "compensation for loss of office".
She left the BBC after her application to become director-general was rejected and also took a "tax-free cash lump sum" of £251,770 from her pension.
A BBC spokeswoman said: "The remuneration for Tony Hall's new Executive Board will be 8% lower than in 2011/12.
"Excluding one-off exceptional costs the Executive Board remuneration for 2012/13 was broadly level with the previous year."
The accounts also showed spending on top on-screen talent fell, with the number of people paid more than £500,000 dropping from 16 to 14.