The pro-democracy camp is to launch a campaign urging Chief Executive Tung Chee-hwa to appoint a minimum number of district councillors.
The move comes after legal advice indicated that the chief executive needed only name two members to each of the 18 councils.
Meanwhile, the Democratic Alliance for Betterment of Hong Kong, which suffered a huge setback at the polls, said it would be acceptable to reduce the number of appointed seats.
Democrat Sin Chung-kai said advice had indicated that a minimum two appointees to each council would fulfil legal requirements. Secretary for Constitutional Affairs Stephen Lam Sui-lung said on Tuesday that he had yet to receive any legal advice on the issue.
Mr Sin said the pro-democracy camp would soon start a campaign demanding prospective appointees decline if approached by the government.
The campaign would also include a rally on December 7 in Central, a debate in the legislature to be moved by Democratic Party chairman Yeung Sum and a call for a special meeting of the constitutional affairs panel.