A mystery caller has been wrongly telling elderly Melbourne residents they don't have to vote in the Batman by-election, the Labor Party says.
It has prompted Labor to send out 10,000 robocalls and 2400 text messages to older voters, reminding them they must have their say.
"Lying to elderly people is as low as it gets," a Labor spokesperson said on Saturday.
"We're encouraging all Batman residents to ignore these dirty tricks and exercise their right to vote."
Labor said several elderly voters received a call from someone who said people over the age of 70 didn't have to vote in Saturday's by-election.
The party contacted the Australian Electoral Commission, which promptly sent a Tweet saying voting was compulsory for everyone enrolled in Batman.
Labor's Ged Kearney and Greens candidate Alex Bhathal are going head-to-head in a tight contest for the inner-Melbourne seat.
The by-election stands as a test of whether the Greens' march into inner-metropolitan seats continues, or Labor can appeal to a younger "hipster" demographic.
It comes after Labor MP David Feeney resigned over his dual citizenship status.
