POLICE associations have been reminded they can contact China's working committee on Hong Kong's transitional matters only in an unofficial capacity. The advice came after the Preliminary Working Committee (PWC) announced last week that it would establish a study group on civil servants. The major staff associations, representing superintendents, local and expatriate inspectors and junior officers, were informed on Friday that they could liaise with the PWC only in a private capacity. Chairman of the local inspectors' association, Robert Chau Chuen-kung, said he was reminded that ''the Joint Liaison Group is the formal channel between the China and Britain Government over matters of Hong Kong'' and that officers ''should not be members of any PWC groups or the PWC''. The Deputy Secretary for the Civil Service, Thomas Tso Man-tai, said: ''The Government's position remains that it is up to the individual unions' consideration whether they should have contact with the PWC members.'' The Government had also informed staff about their position through the departments or the central consultative councils (management and staff). But staff unions were not sure whether they should join the working group if invited. Mr Chau said they should not join as government servants, because the group was endorsed by the Beijing Government. The Senior Non-Expatriate Officers' Association vice-president, Au Chi-keung, said he had agreed to have discussions with the group members on some issues but it was to be further considered whether they become members. The Disciplined Services Council chairman, Philip Sin Ping-yung, agreed they should join because the transition was a matter for all Hong Kong people. A directive was issued early this year by the Government banning the unions from liaising with the PWC. Its position later changed to permit them to have contact only through the union or in a private capacity.