A parliamentary committee examining the 2025 election is also reviewing whether Australia needs more MPs as the population increases and representatives are responsible for an increasing number of constituents.
Each electorate covers about 120,000 voters, and thousands more constituents not on the ballot.
The coalition will oppose any move to increase the number of MPs in federal parliament, saying it will cost taxpayers too much when Australians were dealing with cost of living pressures.
Labor hasn't released any policies on the issue, and Special Minister for State Don Farrell has said he would wait for the committee's findings before pressing ahead with any changes.
The prime minister branded questioning from Opposition Leader Angus Taylor in parliament about the issue extraordinary at a time when there was war in the Middle East and significant economic impacts stemming from it.
"I am satisfied with the current number of seats in the House of Representatives, that is 150 ... with 12 senators from each state," he told parliament on Tuesday, although didn't expressly rule out any changes.
Mr Taylor put the figure for the expansion at $620 million, including salaries, staff, travel and office costs based on an additional 24 lower house MPs and 14 senators, as calculated by the Parliamentary Budget Office.
"Now is the time to tighten the belt, not expand the bureaucracy," he said.
A spokesperson for Senator Farrell said the only party concentrating on the issue or having policies costed was the coalition, as the government remained focused on fuel security and cost of living relief.
"This is clearly not about the policy or issues. It's about the internal audition for attention in the coalition," the spokesperson said.
Labor can still pass laws increasing the parliament without coalition support, with a supportive crossbench in the Senate and a majority in the lower house, but Senator Farrell has signalled he wanted cross-party support.
The committee has been presented with evidence of the need to expand parliament to keep up with demand from constituents, as well as the need for fairer representation for the territories, which only have two senators compared to each state's 12.
Independent ACT senator David Pocock said the point of the upper house was to balance representation between bigger and smaller states and give the latter a more equal voice.
For example, Tasmania has 576,000 people - as at September 30, according to the Australian Bureau of Statistics - and 12 senators, while the ACT has 486,000 people and two upper house members.
