Secretary for Constitutional & Mainland Affairs Stephen Lam estimates at least $150 million will be required if by-elections for all five Legislative Council geographical constituencies are held at the same time.

He told lawmakers today if vacancies arise in all five constituencies, the scale of the by-election will be similar to a District Council election.

Apart from the 530 polling stations required, such as during last year's LegCo election, 30 more polling stations will be needed in penal institutions and Police stations - 70 more polling stations than the 2007 District Council election.

"The amount of election expenditure is directly proportional to the number of electors and the number of polling stations. Therefore, if in 2010 we have to arrange by-elections for five geographical constituencies, then the final expenditure may exceed $150 million," he said.

As the provision of the Registration & Electoral Office will not be sufficient for by-elections of this scale, the office will have to seek funding from LegCo to hold the polls.

He said the Government has the constitutional responsibility to hold by-elections when vacancies arise in the LegCo membership, adding the vacancies do not affect LegCo's power to transact business or the validity of its proceedings.