British Museum director Hartwig Fischer has said he will step down from his role, after treasures were stolen from the London institution.
In a statement, he said it was evident the museum "did not respond as comprehensively as it should have" when it was told about the thefts in 2021.
Mr Fischer also withdrew remarks he made earlier this week about the art dealer who first alerted museum bosses.
He said he expressed "sincere regret" over the "misjudged" comments.
The museum announced last week that it had sacked a member of staff after treasures were reported "missing, stolen or damaged".
Earlier this week, Mr Fischer defended the museum's investigation in 2021, when it had told antiques dealer Ittai Gradel that "all objects were accounted for".
Mr Fischer said he had "reason to believe" Dr Gradel had withheld information on other missing items, a comment Dr Gradel said was "an outright lie".
Dr Gradel told BBC News on Friday that Mr Fischer's resignation was "the right thing to do, I think he should have done it sooner but I do accept his apology".
Mr Fischer, who has held the position since 2016, said he would step down as soon as the museum's board had found an replacement.
He had previously announced he would leave the position, but he was not due to depart until 2024.
Deputy Director Jonathan Williams has also agreed to step back from his normal duties until an independent review into the thefts at the Museum has concluded.
"Over the last few days I have been reviewing in detail the events around the thefts from the British Museum and the investigation into them.
"It is evident that the British Museum did not respond as comprehensively as it should have in response to the warnings in 2021, and to the problem that has now fully emerged. The responsibility for that failure must ultimately rest with the director.
"I also misjudged the remarks I made earlier this week about Dr Gradel. I wish to express my sincere regret and withdraw those remarks.
"I have offered my resignation to the chairman of the trustees, and will step down as soon as the board have established an interim leadership arrangement. This will remain in place until a new director is chosen.
"The situation facing the Museum is of the utmost seriousness. I sincerely believe it will come through this moment and emerge stronger, but sadly I have come to the conclusion that my presence is proving a distraction.
"That is the last thing I would want. Over the last seven years I have been privileged to work with some of the most talented and dedicated public servants.
"The British Museum is an amazing institution, and it has been the honour of my life to lead it."
George Osborne, the former chancellor who is now the chairman of the museum's trustees, said Mr Fischer's resignation had been accepted.
He added that Mr Fischer had acted "honourably in confronting the mistakes that have been made".
"No one has ever doubted Hartwig's integrity, his dedication to his job, or his love for the museum," Mr Osborne said.
He added the trustees would ensure the museum had the "necessary leadership to take it through this turbulent period as we learn the lessons of what went wrong".
"I am clear about this: we are going to fix what has gone wrong," he added. "We will learn, restore confidence and deserve to be admired once again."
The museum was first warned by Dr Gradel of thefts from its collection two years ago.
Emails seen by the BBC suggest he had become suspicious when he "stumbled" upon a photo of a Roman cameo fragment that he said had been put up for sale online.
He suggested the item had previously been listed on the museum's website but had since been removed.
The museum said it would investigate, but when Dr Gradel sent emails to follow up on progress, he accused Mr Fischer of "sweeping it all under the carpet".
Earlier this week, a man was interviewed by the Metropolitan Police in connection with the thefts. No one has been arrested.
According to the PA news agency, the missing items are believed to have been taken over a "significant" period of time.
Some of them reportedly ended up on eBay, being sold for considerably less than their actual estimated value.
None of the treasures, which dated from the 15th Century BC to the 19th Century AD, had recently been on display and had been kept primarily for academic and research purposes, the museum said.
The majority were kept in a storeroom.
British Museum thefts: What we know so far
How easy is it to steal treasures from a museum?
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