Former prime minister Tony Abbott has slammed his successor Malcolm Turnbull over the latest changes to the government's energy policy, accusing the PM of breaking promises and telling him: "It is no way to run a government."

Mr Abbott was responding to a number of changes to the National Energy Guarantee revealed late on Friday, including a proposal to set the national emissions reduction target by ministerial discretion rather than locking it into legislation.

Leading the charge against the NEG: Tony Abbott in Parliament this week. Credit:Alex Ellinghausen

The modifications were crafted in a bid to win the support of dissidents in the Coalition after a week of infighting in which nearly a dozen MPs threatened to cross the floor and vote against the NEG.

But Mr Abbott told 2GB radio on Saturday the revised NEG was "the last thing we should be doing" because it gave a future Labor government the opportunity to lift the emissions reduction target without the assent of Parliament.