Several leading museums may be investigated by the Museums Association after claims that they might have broken its code of ethics regarding sponsorship.

The Guardian reports that internal documents from institutions including the British Museum and the National Portrait Gallery suggest that the oil company BP may have exerted undue influence on their operations.

The documents, which include emails, have been obtained through the Freedom of Information Act by the Art Not Oil coalition, who aim to end oil sponsorship of the arts. The coalition have compiled their findings in a report which states that it has identified “inappropriate influence by BP in three key areas: curatorial decision-making, security procedures and opportunities for influence over policymakers.”

So far all institutions have denied claims that BP has interfered in their decision-making. BP has responded that it “never seeks curatorial influence”.

Alistair Brown, policy officer at the Museums Association, told the Guardian that its code of ethics encouraged museums to act transparently. Article 1.2, for instance, says that all those who work in and with museums should “resist attempts to influence interpretation or content by particular interest groups, including lenders, donors and funders.” He added that “the Museum Association’s ethics committee will consider Art Not Oil’s claims if they wish to seek further guidance on this matter and will contact all parties involved to seek their views.”