 A by @-@ election is an election held in between general elections to fill a vacant parliamentary seat . Article 49 of the Constitution states that a vacancy not due to a dissolution of Parliament " shall be filled by election in the manner provided by or under any law relating to the Parliamentary elections " . However , when a vacancy arises in a GRC , no election needs to be held unless all the MPs have vacated their seats . The Prime Minister has full discretion with regards to the timing of the by @-@ election and he is not obliged to call a by @-@ election within any fixed timeline . 
