A spokesperson for Mr Turnbull said the Prime Minister has phoned Mr Shorten expressing his support for the idea.

The pair plan to discuss the issue further when they next meet.

Earlier, Mr Shorten labelled the three-year electoral cycle as "out of whack" with the states, which have four-year terms.

The Labor leader says the nation needs the certainty and longer-term policy making that lengthening the election cycle from three years would bring.

"Governments can be more daring and more determined if they're not constantly thinking about the next election," Mr Shorten told ABC TV on Sunday.

"What this country needs is long-term policy making, over the cycle of polls and 2.5-year (election) cycles."

Referendum required to bring about change to federal electoral cycle

Many of the states and territories now have fixed four-year parliamentary terms, but changing the federal timetable requires a referendum as the three-year term is set out in the constitution.

One hurdle has been the assumption moving to four-year terms would be matched with a corresponding change to elect senators for eight years when at the moment they are chosen for six.

Fear four-year term could lead to 'lazy' governments

Mr Shorten said that shouldn't be a "deal-killer" and other options could be looked at.

Earlier in the year, Liberal backbencher David Coleman flagged a private member's bill to bring in fixed four-year terms, also saying it would allow longer-term planning and deliver more certainty for business investors.

But Special Minister of State Scott Ryan, who oversees electoral reform, said at the time he didn't support the idea and believed it could lead to "lazy" governments.