The British Museum has appointed the National Portrait Gallery head, Nicholas Cullinan, as its new director, after it emerged last year that hundreds of objects had been allegedly stolen from the museum’s collection. Cullinan replaces Hartwig Fischer, who resigned as director last year after accepting responsibility for the museum’s failure to properly respond to warnings about the suspected thefts of hundreds of gems and jewellery. The 46-year-old art historian and curator takes over from the interim director, Sir Mark Jones, the former head of the Victoria and Albert Museum, who stepped in to lead the museum after Fischer’s resignation. Cullinan, whose appointment was approved by the board of trustees and Rishi Sunak, will take up the role in the summer. He said: “One of the greatest museums in the world, it is an honour to become the next director of the British Museum. I look forward to joining its wonderful and dedicated staff and to work with its hugely impressive board in leading it into a new chapter. “This will encompass the most significant transformations, both architectural and intellectual, happening in any museum globally, to continue making the British Museum the most engaged and collaborative it can be.” The most pressing issue Cullinan faces is the fallout from a finding last year that about 1,800 artefacts from the museum collection were “missing, stolen or damaged”. The museum also faces increased pressure to repatriate contested artefacts. The new director will have to address the diplomatic row over the Parthenon marbles. Christos Tsirogiannis, an expert at identifying looted antiquities, said he was still waiting to begin an audit of the museum’s entire antiquities collection after being granted permission to conduct the research by its interim director last September. In response to Cullinan’s appointment, Tsirogiannis, who heads illicit antiquities trafficking research for the Unesco chair on threats to cultural heritage at the Ionian University in Corfu, added: “Any director should be judged from his actions and their results. The British Museum needs primarily to change its mentality in the way it is safeguarding and exhibiting objects, in the way it is behaving to the countries these objects came from and to academics who are trying to conduct research on questionable antiquities in the museum’s collections.” Cullinan also faces pressure over the British Museum’s continuing partnership with BP. As director of the National Portrait Gallery, he ended its long-running partnership with the oil giant. But in his new role, he will inherit the British Museum’s 10-year, £50m partnership with the company, announced in December. The deal will help fund the modernisation of the museum’s grand but ailing building in Bloomsbury, central London, culminating in a redisplay of the entire collection, a project estimated to cost £1bn. Isobel Tarr, a co-director of the campaign group Culture Unstained, said: “After mounting public pressure, Nicholas Cullinan deemed BP to be on the wrong side of the ‘ethical red lines’ when he was director of the National Portrait Gallery, ending their long-running partnership with BP, one of the world’s biggest polluters, and setting up an ethics committee to vet future sponsors. “An urgent question for him as director of the British Museum is, will he draw any similar ‘ethical red lines’ at the museum, which just accepted £50m from BP? Cullinan must urgently address this by ending this indefensible sponsorship deal, and setting the British Museum up for more ethical and sustainable partnerships going forward.” Cullinan was appointed director of the National Portrait Gallery in April 2015 and oversaw the three-year refurbishment of the Trafalgar Square museum and its reopening. He previously worked at the Metropolitan Museum of Art in New York and Tate Modern in London. George Osborne, the chair of the British Museum, said the trustees chose Cullinan as he “brings proven leadership today and great potential for tomorrow”. “I could not be more thrilled for Nick and more excited for us as we enter this new chapter in the long story of the British Museum with confidence, and back on the front foot.” The culture secretary, Lucy Frazer, said: “I look forward to Nick sharing his vision for the museum, including how he will strengthen its world-leading partnerships, deliver the next phase of its major capital project, and ensure the museum’s magnificent collections are enjoyed for generations to come.” Cullinan’s appointment comes after a judge on Tuesday ordered a former curator who the British Museum alleges stole or damaged artefacts, and sold hundreds of them on eBay, to return any items still in his possession. Peter Higgs, the museum’s curator of ancient Greek collections and the acting head of the Greece and Rome department, was sacked last year after the alleged thefts were revealed. Mrs Justice Williams made an order at the high court in London on Tuesday saying Higgs must list or return any stolen items within four weeks. The British Museum had recovered 356 items so far, the hearing heard. Higgs, who disputes the claims, did not attend the hearing due to poor health, the court heard. The Metropolitan police are investigating the alleged thefts, but a spokesperson said it had not charged anyone in connection with the missing artefacts.