Chief Executive Donald Tsang has expressed deep regrets over the resignation of five lawmakers to pursue a so-called "referendum campaign in the five geographical constituencies" through by-elections.

In a statement issued today Mr Tsang said mainstream public opinion has reservations over the move, and many see it as an abuse of the by-election mechanism and a waste of public resources.

"Despite calls for halting the plan, the Legislative Council members concerned have insisted to go astray. Legislators should discharge their constitutional duties in the legislature with dedication. They should not resign lightly," Mr Tsang said.

He reiterated the so-called "referendum" is inconsistent with the Basic Law, noting it has no legal basis or legal effect and the Government will not recognise it. The general public does not want unnecessarily provocative statements which might lead to social division.

A consultation on the methods for selecting the Chief Executive and for forming LegCo in 2012 is under way. Unnecessary resignations will not help the community forge consensus on constitutional development, he added.

"As the Chief Executive I would not want to see what has happened today. The Government, however, has the responsibility to act in accordance with the law and hold by-elections following the relevant legislation. We will inform LegCo later of the detailed arrangements for holding the by-elections."

Secretary for Constitutional & Mainland Affairs Stephen Lam said $150 million in public funds will be required to organise a by-election, amounting to $30 million for each of the five resignations.

Five legislators from the League of Social Democrats and the Civic Party tendered their resignations to the LegCo Secretariat today.