The panel is investigating a series of events that undermined confidence in the commission last year, including dismissal of a director of operations, and which culminated in the resignation of its chairman, Michael Wong Kin-chow.

Human Rights Monitor wants to know if Dr Ho, who appointed the panel, will appear before it.

Mr Harris said the non-profit group was seeking details about the selection process and evidence of its impartiality.

'How many persons were approached before a decision was taken to appoint the present panelists?' he wrote. 'We would also like to know under what legal provisions, if any, the panel was appointed, and whether its members receive remuneration or allowances.'

If the panel was biased, the process 'needs to be repeated and if necessary different persons selected to carry out this important inquiry', the letter said.

The questions raised by Human Rights Monitor follow similar doubts expressed late last month, when Christina Wong Wai-yin, of the Women's Coalition, said she was not convinced the inquiry would be neutral.

The Democratic Party also said it would request a special committee be established in the coming legislative year to conduct an investigation.

The panel comprises three independent members but is supported by a secretariat including a former district officer for Shamshuipo and a retired civil servant.

Dr Ho has defended the panel's independence and insisted the Home Affairs Bureau had no influence or relationship to the secretariat.

A spokeswoman for Dr Ho said he would not be able to immediately comment as he was on an official visit to the mainland and will return tomorrow.

The controversy began after Mr Wong, a retired Court of Appeal judge, succeeded Anna Wu Hung-yuk as chairman a year ago. His appointment drew scrutiny as he had little experience in equal opportunities and human rights.

Other moves also caused worry, including the sacking of a key staff member appointed by Ms Wu.

In the midst of the controversy, other board members, including Raymond Wu Wai-yung, were reappointed even though several groups had nominated other more experienced candidates.

Ms Wu questioned last month the direction of the panel's questioning. She said it appeared to be seeking information related to her oversight of the EOC rather than the series of events that led to a public crisis of confidence.