Australia's largest electricity generator has strongly dismissed a new push by the Turnbull government to make the country's coal-fired power stations run for years longer than originally planned.

Prime Minister Malcolm Turnbull raised the prospect in Parliament – and in a phone call to AGL chief executive Andy Vesey – after a new report from the nation's energy regulator warned urgent action was needed to stop homes and businesses losing power during extreme summer heat.

Mr Turnbull has revealed that the government wants NSW's 46-year-old Liddell plant to remain operating for "at least" another five years beyond its scheduled 2022 closure.

But the Prime Minister was rebuffed only hours later when Mr Vesey said in a series of tweets the company was "getting out of coal" and that it was committed to the closure date.