Who may file a complaint?

Electoral Act 1968, 116

A petition complaining of an undue return or an undue election of a Member for any constituency by reason of want of qualification or by reason of disqualification, corrupt or illegal practice, irregularity, or by reason of any other cause whatsoever, may be presented to the High Court by.

(a)        a voter in that constituency; or

(b)        any person who was a candidate at such election:

Provided that a petitioner shall, before lodging his petition with the Registrar of the High Court, afford every person, other than the Member whose election or qualification is complainedof (hereinafter referred to as 'the respondent'), who was a candidate at the election to which the petition relates an opportunity of becoming a party to the petition as a co-petitioner.

http://aceproject.org/regions-en/eisa/BW/Electoral%20Act%201968.pdf