More than 120 voters have been referred to the police for voting twice in September's general election.
The Electoral Commission said dual voting is an offence under the Electoral Act.
126 individuals voted twice at the 2014 election - double the number of the 2011 election.
The Commission said most of those who voted twice had cast an advance vote and then voted again on election day.
Voting more than once carries a penalty of a jail term of up to two years and/or a fine of up to $40,000. However, police have discretion over whether to prosecute.
In 2011, 63 referrals were made to police - 32 people were given warnings, 29 were cleared and only two remained unresolved.