The issue was at the heart of months of mass protests in the former British colony where pro-democracy demonstrators blocked off stretches of main roads to call for true universal suffrage.
Albert Ho's announcement that he would resign his seat in the city's Legislative Council is the latest show of defiance by Hong Kong's pro-democracy lawmakers, who have vowed to veto any government proposal over how to choose a new leader in 2017.
Though Hong Kong will choose its chief executive through a one-person-one-vote system, the authorities have said candidates must be vetted by a pro-Beijing committee.
Ho's resignation from his "super seat", one of five in the legislature, will trigger a city-wide by-election in which five million people are eligible to vote.
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"I think I should take every possible opportunity to enable the Hong Kong people to vent their anger, their frustrations, and protest against the central government," Ho told reporters, announcing his decision.
Ho said he would resign after pro-democracy lawmakers, who hold a critical legislative veto on constitutional amendments, vote down the political reform package.
Lawmakers are expected to vote on the package in the early months of the summer, but experts have questioned the usefulness of Ho's move.
"It (the resignation) would be meaningless because the bill would have been voted down already," political analyst Sonny Lo told AFP.
Government officials have themselves expressed pessimism over the package's successful passage.
"The political reform is now looking like mission impossible," the city's justice minister Rimsky Yuen told media early today, admitting there would be "difficulty" in securing the necessary votes.