Labor has signalled it could support a royal commission into Australia’s power companies if the terms of reference included analysis about whether the privatisation of electricity assets has driven up energy prices.

The Labor leader Bill Shorten told reporters in Brisbane that Australians needed the energy companies to “explain why there shouldn’t be a royal commission, and so far they haven’t”.

He said if a royal commission was to go ahead, it would have to include analysis about the impact of privatisations on power prices. “I do think it’s long past time to have an examination of whether the privatisation of the electricity systems in Australia is a good idea.”

While giving the idea tacit support, Shorten said “the biggest single driver of energy prices in this country going up” was a lack of policy certainty from the commonwealth. “We’re not getting investment in energy generation that would decrease the price because people don’t know what the rules are.”

Shorten’s comments follow a signal by the prime minister Scott Morrison that he could countenance a royal commission into Australia’s power companies.

Morrison used a radio interview on Monday to signal he was “open” to a royal commission – an idea that Peter Dutton floated before trying to seize the Liberal party leadership.

“There has been no shortage of inquiries into the energy industry Sarah McNamara

The government dumped its signature energy policy, the national energy guarantee, as the preamble to the leadership crisis which saw Malcolm Turnbull lose the top job.

Morrison has declared since taking over the Liberal leadership that the government’s focus is on delivering lower power prices, and he’s been seeking a quick fix, partly by threatening market interventions, including breaking up power companies if there’s no action on prices.

The organisation representing Australia’s major power companies said there was no need for a royal commission because they had just opened their books to the competition watchdog.

“There has been no shortage of inquiries into the energy industry,” said the Australian Energy Council’s chief executive Sarah McNamara.

“We have just spent 15 months working with the Australian Competition and Consumer Commission on its forensic review. That inquiry compelled 10 years of data from power companies”.

McNamara said the ACCC had brought forward more than 50 recommendations for reform, some of which the government had already adopted, and another inquiry by the competition watchdog would run until 2025.

“It is not clear what taxpayers would learn from a royal commission that we haven’t already learnt from the ACCC’s extensive review.”

Last week, McNamara made the same conceptual point as Shorten – declaring the main reason electricity prices are high for Australian consumers is a decade-long vacuum in energy policy – not misconduct in the market.

Labor on Monday also proposed stronger export restrictions on gas, promising to help reduce energy costs by reserving more domestic supply. Shorten has floated a permanent gas export control trigger that can be pulled when gas prices are too high, not just when a gas shortfall is forecast.

The federal Labor leader also called on the states to end the current moratoria on exploration for conventional gas, including the Labor government in Victoria, which will go to the polls in November.

“Our policy to have export controls, to have a national interest test, to encourage the extraction of more gas, is going to deliver cheaper energy to Australian business and is going to secure Australian jobs,” the Labor leader said.