Bill Shorten's call for fixed four-year terms for federal governments could become a reality after Malcolm Turnbull threw his support behind the plan to overhaul the nation's electoral system.

Shortly after the Opposition Leader called for a new bipartisan push for a referendum to change the constitution, the Prime Minister phoned him to express his personal support for the change.

A spokeswoman for Mr Turnbull later said the pair spoke briefly about "several matters", including the four-year term proposal. "The two agreed to discuss the matter further when they next meet," she said.

Earlier, the Labor leader said the three-year electoral cycle of the federal system was "out of whack" with the states, which have mostly adopted fixed four-year terms, and too often led to "short-term" policy making.

Signalling he intends to elevate the issue - which he has previously indicated was not a priority despite its place in the Labor Party platform - Mr Shorten said he wants both major parties to take the policy to the next election and then work together to deliver a referendum regardless of who wins.

The call is likely to resonate with a number of Coalition MPs who have also called for fixed four-year terms, most recently Liberal MP David Coleman.

"I think that the nation needs four-year terms," Mr Shorten told the ABC's Insiders program. "What this country needs is long term policy-making. Governments can be more daring and determined if they're not constantly thinking about the next election."

Mr Shorten said the average lifespan of a federal government is currently about 2½ years - not long enough to deliver on an ambitious agenda.

Under the current system, federal elections must be held within three years of a new parliament's first sitting. However, prime ministers have the power to call an early election at virtually any time, giving them the power to manipulate election timing for their own political gain.

Labor has long promised to reform the system but successive leaders have failed to progress the policy.

In 2007, Kevin Rudd pledged a referendum, calling the current system an "antique". He even set aside $27 million in the budget for the poll but later abandoned the idea. Julia Gillard reignited debate about fixed terms in 2013 when she decided to name an election date eight months in advance but she too shied away from pursuing fixed four-year terms.

But despite his enthusiasm for the idea, Mr Shorten says a referendum will fail unless the major parties are on a unity ticket.

"Perhaps both sides of politics could sign up to a commitment to jointly support, regardless of who is in charge after the next election, four-year terms in the constitution. That [is the] sort of certainty which I think people are looking for."

A major stumbling block in past has been that such a change would extend Senate terms from six years to eight but Mr Shorten said that need not be a "deal killer".

Proponents of the change have long argued that fixed four-year terms would give governments more time to find their feet and keep them focused on governing rather than election wargaming.

At the state level, both Labor and Liberal governments have introduced fixed terms. Overseas, most comparable parliaments have four- or five-year terms, many of them fixed. The UK recently introduced fixed five-year terms.

In 1988, the Australian public rejected Bob Hawke's referendum proposal for non-fixed four-year terms but more recent polling has shown support for change.