The Liberal and Labor parties say they will comply with new rules asking federal election candidates to declare they are eligible to sit in parliament.
The regulations are due to be put to parliament next week, but filling out the new form won't be compulsory for candidates.
However, senior spokesmen for the Liberal and Labor parties told AAP the candidates for the five by-elections due to be held on July 28 would fill out the forms and publicly release them.
The commitment comes as Malcolm Turnbull rejected suggestions the date chosen for the by-elections was a political ploy aimed at clashing with Labor's national conference, which was scheduled for that weekend.
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.
He said the AEC was impartial and non-partisan.
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.
But Opposition Leader Bill Shorten said the "sneaky" delay will leave about 500,000 people without representation in the federal parliament for three months.
He insisted the date was selected by the government, which he said had no problem ensuring by-elections happened quickly last year when coalition MPs were forced to resign.
Senior Labor leaders met on Friday afternoon and decided to move the national conference to another date.
"The decision to schedule them on the same date as Labor's Conference is blatantly partisan," Labor frontbencher Mark Butler said in a statement.
"The national executive will meet next Wednesday to determine the earliest practicable date for a rescheduled conference."
The polls in Longman, Braddon, Fremantle and Mayo were triggered by resignations of three Labor MPs and an independent due to their dual citizenship, while Perth Labor MP Tim Hammond resigned for family reasons.
