The director of the British Museum, Hartwig Fischer, has announced he is stepping down with immediate effect following alleged thefts of artefacts from the central London institution.

Mr Fischer said the situation is “of the utmost seriousness” and he has “sadly come to the conclusion” that his presence is “proving a distraction”.

The museum earlier sacked a senior curator after close to 2,000 artefacts, worth millions of pounds, were believed to have been stolen.

Mr Fischer said it was “evident that the British Museum did not respond as comprehensively as it should have” in response to “warnings in 2021” about a problem that has now “fully emerged”.

“The responsibility for that failure must ultimately rest with the director,” he said.

Mr Fischer also said he had “misjudged” some comments he made about antiques dealer Ittai Gradel.

He added: “I wish to express my sincere regret and withdraw those remarks.”

Dr Gradel has said his concerns about misplaced items were ignored.

He said: “I told them about the few items where I had absolute proof that they came from the British Museum. I said, ‘I have all the information you would require me, all the assistance, I’m entirely at your disposal’. They never contacted and now they’re trying to shoot the messenger,” he said.

Mr Fishcer previously said that an “individual who raised concerns” had “many more items in his possession”.

He added: “It’s frustrating that that was not revealed to us as it would have aided our investigations.”

Former chancellor George Osborne, who chairs the museums trustees, said “no one has ever doubted Hartwig’s integrity, his dedication to his job, or his love for the museum”.

He added: “I am clear about this: we are going to fix what has gone wrong. The museum has a mission that lasts across generations. We will learn, restore confidence and deserve to be admired once again.”