Victoria's corruption watchdog has made a public appeal for witnesses who saw a police raid on a queer bookshop in Melbourne, which led to the serious injury of a man.

Nik Dimopoulos required intense arm and shoulder surgery after officers stormed the Fitzroy shop in the early hours of May 11, wrongly arresting him as they searched for an offender.

Officers from the Critical Incident Response Team raided the Hares & Hyenas bookshop in Fitzroy in May and arrested Nik Dimopoulos in a case of mistaken identity. Credit:Scott McNaughton

Independent Broad-based Anti-corruption Commissionchief Alistair Maclean on Wednesday said an investigation into the raid is ongoing and witness accounts are essential.

"CCTV footage of the vicinity shows there were a number of people in the area at the time of the incident, however our efforts to contact these potential witnesses have been unsuccessful," Mr Maclean said.