Constitutional expert Professor George Williams has written to the parliament's electoral matters committee, which is undertaking an inquiry into the 2019 election, arguing for an overhaul of early voting rules.

At this year's election a record 4.76 million early votes were cast, plus about 1.5 million postal votes.

Electoral laws allow voters to cast their ballots early if they will be far from a polling booth on election day, are travelling, in prison, at work, about to give birth or it may conflict with their religious beliefs.

However, in practice electoral officers give voters the benefit of the doubt if they request an early vote.

Prof Williams said millions of Australians had elected MPs based on "incomplete information" during the 2019 election.

"Much of the electorate cast their ballot before Labor released its election costings and Prime Minister Scott Morrison launched his campaign," he wrote.

"The lack of information can prove decisive, especially in close contests where votes may have shifted if people were exposed to the full suite of policies and campaign gaffes, or where candidates were disendorsed."

The period of pre-poll voting should be two weeks, at the most, in line with NSW and Victoria, he said.

Better checks could be put in place to ensure pre-poll voters have a genuine problem getting to the ballot box.

"A simple requirement to provide some form of evidence may turn many people away from pre-poll voting," Prof Williams said.

In the longer term, parliament should consider the idea of an "election week", rather than a single election day, which would provide plenty of time to get to the polls.

Alternatively, online or telephone voting would be beneficial.

Australian Associated Press