Lawmakers say new guidelines concerning conflict of interest involving ministers are flawed because they fail to stipulate penalties for a failure to comply.
Last year an independent committee chaired by former chief justice Andrew Li Kwok-nang suggested that any political appointee who failed to declare his or her interests might be subject to punishment ranging from a warning to suspension.
Li's panel also said that the chief executive should be covered by the same rules regarding the acceptance of advantages.
Again, this recommendation was not taken up.
Civic Party lawmaker Dennis Kwok said that as the new rules did not mention any punishment, it would do little to improve the system.
Democratic Party chairwoman Emily Lau Wai-hing said: "The administration should clarify in a press conference how it will enforce the new guidelines and why certain suggestions recommended by Justice Li were not accepted."
Former civil service minister Joseph Wong Wing-ping said he was worried because ministers who thought they might have a conflict of interest would not have to tell the public.
A minister would be obliged to report a potential conflict to the chief executive, while undersecretaries or political assistants would tell their supervising chief.
The new rules were drawn up in the aftermath of several cases that culminated in the resignation of three of Chief Executive Leung Chun-ying's officials and executive councillors.
In May, Leung's top aide, Barry Cheung Chun-yuen, quit his official posts after he came under a police probe into the collapse of his Hong Kong Mercantile Exchange.
Cheung was recently sued for HK$40 million arising from loans his company took out.
Last Thursday, another Exco member, Franklin Lam Fan-keung, stepped down after nine months' leave of absence - prompted by criticism that he made use of insider information to sell two flats ahead of new stamp duties. The justice department decided not to prosecute him over allegations of misconduct in public office.
A day later, Henry Ho Kin-chung, political assistant to development minister Paul Chan Mo-po resigned after failing to declare his family's land stake in the proposed Kwu Tung new town area he once held with family members through a private company.
Chan has also faced calls for him to go, after his wife and her family were revealed to own land in the same area.
Democratic Party chief executive Lam Cheuk-ting, who is a former anti-graft investigator, said the government should also regulate non-official executive councillors under the new guidelines.