The Australian Electoral Commission has written to political parties and candidates about the issue, amid reports of wrong forms being distributed to voters in one division and the AEC's purple colour being used on forms in another.

"It's legal but it is potentially misleading and we're concerned," AEC Commissioner Tom Rogers said in a statement on Saturday.

"While we haven't seen unauthorised postal vote applications, the use of colour and wording means someone who doesn't examine the material in detail could mistake it for a piece of AEC communication."

Mr Rogers said the election mainly involved people voting in person so there was no need for the mass distribution of postal ballots.

He urged those who needed a postal vote for the May 21 election to contact the AEC directly.

"Political parties send postal vote applications to residents every election but the increased variation of channels and wording this election, combined with the environment, is of concern," he said.

"Our message couldn't be clearer - vote in person if you can, apply for a postal vote through us if you need one."

Voters can apply for a postal vote via the AEC's website, with applications closing on May 18.

Australian Associated Press