Ministers are looking at providing support for household bills next winter, Keir Starmer said, as he suggested the energy price shock unleashed by the Iran conflict could continue for months to come.

The prime minister indicated he would prefer to focus any taxpayer-funded help on the poorest households, rather than an expensive universal bailout, ahead of an emergency meeting on the economic fallout of the Middle East crisis.

Addressing the Commons liaison committee on Monday, he said there would not necessarily be a “quick and early end” to the conflict, despite Donald Trump postponing US strikes on Iranian power plants.

Starmer promised to look at “every lever that’s available” to help people cope with the cost of living impact, with ministers understood to be discussing contingency plans at the Cobra meeting, which will be attended by the governor of the Bank of England.

“We’re looking across the board at what can be done, whether it’s cost of living or the support we need to put in. I want to make sure we’ve examined all the appropriate levers that we can pull,” said Starmer.

Rachel Reeves is expected to update MPs on Tuesday on her plans to improve the security of UK energy supplies, as well as giving a broader assessment of how the UK economy is coping with the shock of the Middle East crisis. But she will not announce specific support packages for consumers.

Instead, ministers are working on means-testing support when the next energy price cap comes to an end in June, as well as when the following one starts in the autumn, and energy consumption and bills are higher.

“We’re looking at in the first instance what happens when the current price cap ends, which is the end of June,” Starmer said.

“I think the one we’re equally focused on is the one after that, because the June to September/October period is when only about 77% of energy is used within households. It’s after that it gets very heavy.”

But he suggested there would be no repeat of Liz Truss’s universal bailout at the time of Russia’s invasion of Ukraine, which government insiders estimated cost about £40bn.

“I’m acutely aware of how much it cost last time round, and I’m acutely aware of the state of the public finances, but we will look this afternoon at what the appropriate approach is,” he told MPs.

“There are difficulties in that we don’t yet know the extent of the challenge we’re facing, because we don’t know when this conflict is going to end, but we’re actively looking at what measures we can put in place.”

Ministers are also considering giving the Competition and Markets Authority (CMA) “further teeth” so it can stop companies exploiting the war, the prime minister said.

“On price gouging or profiteering, we absolutely need to bear down on it, so we are actively considering whether the CMA should have additional powers to deal specifically with that. But at the moment, we are making sure they are focused on anti-profiteering steps they can take now.”

He warned that despite Trump’s decision to pause airstrikes on Iran’s power plants after talks between the US and Tehran over the weekend – which Starmer said he had been aware of – the energy crisis could continue.

“All of our focus and energy has to be in the swift de-escalation, but we’ve got to plan on the basis that it could go on for some time,” he said.

Starmer was also quizzed on the publication of the delayed defence investment plan, amid pressure on the government to bring forward defence spending over concerns about the state of the British military after years of under-investment.

He said the plan was on his desk and would be “finalised soon”. But he insisted he would not make commitments until he was clear where the funding was coming from, as he appeared to acknowledge for the first time the Treasury and Ministry of Defence had been at loggerheads.