By Hitesh Tikoo London, Oct 2 : MI5, the UK's domestic counter-intelligence and security agency, risks undermining the confidence of the families bereaved by the 2017 Manchester Arena terror attack by asking to provide evidence anonymously and from behind a curtain, a public inquiry has heard. Lawyers representing the families of victims from the May 22, 2017 bombing, which killed 22 and injured hundreds others, complained that the agency had an "obsessive focus on secrecy" and called on the inquiry chair to insist that its evidence be heard openly. During the inquiry's open proceedings, MI5 has offered to put up a single witness, a senior officer known as Witness J. However, the agency wants him to remain anonymous and give evidence from behind a screen visible only to the judge. Speaking at a preliminary hearing of the public inquiry, Pete Weatherby QC, representing some of the bereaved families, said: "Allowing him to remain a mystery in the shadows in these hearings does shake the confidence of the families and no doubt the wider community, including many other survivors." At previous terror attack inquiries, such as the London Bridge attack, the Security Service has put up a senior officer to provide evidence on behalf of the agency anonymously and from behind a screen or a curtain, in part reflecting the fact that MI5 officers largely operate in secret. Neil Sheldon QC, representing MI5, said the agency only ever confirmed the identity of its director general. It was not possible or desirable to have him give evidence, because that would divert him from "the obligations and duties that he has, in respect of national security", the lawyer added. The spy agency argues that it needs the extra time to provide full answers to the inquiry that do not compromise the security of its operations, but the demand was again opposed by lawyers for the victims' families. A compromise was also put forward by Paul Greaney, the counsel to the inquiry. Greaney suggested Witness J could give evidence where he was seen in person by the judge, Sir John Saunders, plus one lawyer representing victims' families, however, the lawyers present said that in that case, each of the victim groups should be represented. It is for Judge Saunders to decide how to handle MI5's public evidence. He is expected to make public his conclusions at a later date. On May 22m 2017, Salman Abedi detonated a shrapnel-laden homemade bomb as people were leaving the Manchester Arena following a concert by US singer Ariana Grande. The Islamic State (IS) claimed Abedi as one of their soldiers. /IANS