Malcolm Turnbull has rejected opposition claims the date set for five upcoming by-elections was a partisan political ploy aimed at clashing with Labor's national conference.
The ALP will change the date of its conference to avoid a clash with the July 28 by-elections, but the prime minister says its Labor's fault the polls will be held so late.
The polls in Longman, Braddon, Fremantle and Mayo were triggered by resignations of three Labor MPs and an independent this month due to their dual citizenship, while Perth Labor MP Tim Hammond resigned for family reasons.
Mr Turnbull blamed Labor for denying for months the legal reality the High Court would rule its MPs ineligible.
"If Bill Shorten had wanted to have the by-elections in these electorates earlier, his members should have done the right thing and resigned last year," he said.
With five by-elections across four states, electoral commissioner Tom Rogers said the "optimal" July 28 date was chosen to avoid school holidays and allow candidates to comply with new regulations to declare they are not dual citizens.
"The decision to schedule them on the same date as Labor's conference is blatantly partisan," ALP frontbencher and party president Mark Butler said on Friday.
But the prime minister said it was outrageous for Labor to infer the Australian Electoral Commission's advice to Speaker Tony Smith was designed to advantage the coalition.
"The electoral commission is utterly impartial and non-partisan," he told reporters on the NSW Central Coast on Friday.
But Mr Shorten said the "sneaky" delay will leave about 500,000 people without representation in the federal parliament for three months.
He insisted the government chose the date to hurt Labor, while single by-elections happened quickly last year when coalition MPs were forced to resign.
"All of a sudden we've got every excuse under the sun why it can't happen quickly," Mr Shorten told reporters in the Brisbane seat of Longman.
There have never been five by-elections held on the one day in Australia.
Senior Labor leaders met on Friday afternoon and decided to move the date of the Adelaide conference, but no new date has been set.
Senior Labor figure Anthony Albanese said it was beyond belief the commission hadn't taken the clash of dates into account.
Mr Albanese accused Mr Rogers of giving confused evidence to a Senate estimates hearing over how he landed on the date.
Cabinet minister Christopher Pyne said voters couldn't care less about the date of the conference.
"I think the ALP looks like a spoilt child at the royal show who hasn't got the ice cream that they asked for," Mr Pyne told Sky News.
