Former treasurer Peter Costello has launched an excoriating attack on the Liberal Party leadership, warning the government is "operating in a parallel universe" by promising voters it would deliver reforms in 10 years' time.

The government's inability to produce a coherent economic story meant the Liberal Party had splintered along the social lines that ultimately contributed to the demise of Malcolm Turnbull as prime minister, he also said.

"I was deputy leader of the Liberal Party for 14 years and I didn’t know that we had a right faction and a left faction and, if we did, nobody invited me to join either of them," Mr Costello said.

Former treasurer Peter Costello. Credit:Josh Robenstone

"One thing you could always unite the Liberal Party around in my time was the economic narrative.