A legal amendment is being considered to prevent Legislative Councillors from resigning to trigger by-elections.

Secretary for Constitutional & Mainland Affairs Stephen Lam today told legislators last month's Legislative Council by-election was as big as a general election and cost taxpayers $159 million.

He said there have been calls from the community to plug the loophole and restrict legislators from resigning to trigger by-elections.

"Consideration will have to be given as to whether these proposals comply with the Basic Law, whether the restrictions are reasonable from the legal point of view, and whether [they are] are practicable.

"After we have completed the research and analysis we will decide how the legislation can be amended. Our plan is to deal with the amendment motions to Annexes I and II to the Basic Law in relation to the methods for selecting the Chief Executive and for forming LegCo in 2012 before the LegCo summer recess in mid-July. Matters relating to local legislation can be dealt with thereafter."