Hogan Lovells has reported former litigation partner Christopher Grierson to the City of London Police for allegedly defrauding the firm of £1m in false expenses claims, it has been confirmed.

The firm notified the police of the alleged fraud within the last 48 hours. Grierson, who is best known for working on the high-profile BCCI litigation, has repaid the full amount to the firm over the last two days.

He was dismissed earlier last month (11 May) following an internal investigation led by the transatlantic firm's finance team. The investigation found evidence of more than £1m in irregular expenses claims made over a four-year period leading up to the end of 2010.

Grierson is currently under investigation by the Solicitors Regulation Authority (SRA) after Hogan Lovells reported the case to the regulator last month.

The regulator was set to present the findings of its investigation – which is likely to take several months – to the Solicitors Disciplinary Tribunal, which will then decide on its response, which could include a financial penalty or disbarment from the profession.

Partners were told about the alleged fraud and Grierson's dismissal last month, with the SRA being initially notified on 11 May. The firm is also reviewing its internal control procedures in light of the investigation into Grierson.

A spokesman for Hogan Lovells said: "Since discovering Christopher's actions our focus has been on promptly investigating and gathering the necessary evidence; being open with partners and our people about what has happened; and notifying the regulator. We have now recovered the money owed to us and have notified the City of London police."

He added: "No clients were affected as a result of Christopher's action. He committed a major breach of trust and we have taken the appropriate action throughout."

The firm's handling of the matter has attracted some external criticism for the decision not to immediately report the alleged fraud to the police. It is understood that Hogan Lovells held back from initially reporting the matter to the police as a criminal investigation would have severely limited its ability to communicate internally with its staff.

The firm has also stressed that it intended to follow a series of steps in its response to the matter and had never ruled out going to the police.