Tony Abbott rushed a promise to hand over $3 billion of East West Link cash despite "clear advice" from the public service that the project hadn't been justified and wasn't ready.

In a damning assessment, federal Auditor-General Grant Hehir​ has revealed Mr Abbott personally approved payments for both sections of the road, signing over half the money, $1.5 billion, on the last day of 2013-14 to maximise the budget deficit pain in Labor's final financial year.

In doing so, the audit report found Mr Abbott ignored clear advice from the Department of Infrastructure and Regional Development that the money was being paid well in advance of project needs, suggesting the decision was taken for political purposes, in the absence of any rigorous assessment.

"The decision to provide $1.5 billion in advance provided budget presentation benefits to the government by bringing forward the payment, which resulted in a larger budget deficit for 2013-14," the assessment said.