She asked for the Constitution to be amended to declare explicitly the right as a fundamental liberty.

Or if not, perhaps convening an advisory tribunal to consider the question.

Article 100 of the Constitution specifies that the President can refer a Constitutional question to a panel made up of at least three Supreme Court judges.

Prof Thio, who teaches constitutional law at the National University of Singapore, made this proposal in Parliament yesterday during the debate on the Law Ministry's budget.

'To affirm and underscore the workings of our system of representative democracy, would the Minister consider taking the desirable step to amend the Constitution to expressly entrench the right to vote in the Fundamental Liberties Chapter?' she asked.

She said that the lack of any clear mention of the right to vote in the Constitution, as well as a 1998 High Court ruling that appeared to refer to the right to vote as a 'privilege', seemed to suggest that it did not have constitutional status.

In that case, the right could be repealed by Parliament.

'Surely, our right to vote cannot depend upon legislative will?' she said. 'This would place something so basic on too tenuous a footing, for what Parliament gives, Parliament can taketh away.'

Law Minister K. Shanmugam will respond to her question as well as those from other MPs on Friday.