Energy Minister Josh Frydenberg has assured Coalition MPs that electricity customers were “through the worst” of the price spikes of recent years, as former prime minister Tony Abbott fired another warning shot over the government’s energy policy.

Mr Frydenberg told Liberal and Nationals colleagues that he expected prices to fall in Queensland and stay relatively flat in NSW and South Australia according to forecasts for the next pricing period from July.

The assurance came as several MPs expressed their concern about energy and Mr Abbott sought an assurance that the government’s policy would go back to the Coalition party room for a decision by all members.

The discussion was another sign of the strains within the federal Coalition as Mr Abbott and like-minded MPs agitate for investments in coal-fired power stations while most others back the National Energy Guarantee agreed by ministers and backbenchers last year.

Mr Frydenberg will take the policy to a meeting with his state and territory counterparts in the second week of August in an essential move to get their approval before the Guarantee can be imposed.

Mr Abbott made this an issue in the regular Tuesday party room meeting by asking Prime Minister Malcolm Turnbull and Mr Frydenberg whether the plan would be put to the party room before it went to COAG.