An inquiry has been launched into the Morrison government's handling of commuter car park grants to target seats before the 2019 election.
The Senate on Tuesday agreed to the finance committee inquiry which followed a scathing auditor-general report into the $660 million Urban Congestion Fund.
The inquiry will examine the allocation of funding and whether its administration met the highest standards of governance and accountability.
As well, it will probe the role of the prime minister's office in determining which projects to allocate funding to and who would announce the projects.
And it will tackle the issue of whether the fund achieved its aims.
Prime Minister Scott Morrison has been reluctant to detail his office's involvement in the fund, which the auditor-general found was not effective or merit-based.
None of the 47 commuter car park sites selected by the government before the 2019 election were picked by the infrastructure department.
Just two of the promised car parks have been completed while some of the projects have been dumped.
Twenty-seven were approved the day before Mr Morrison called the election.
Urban Infrastructure Minister Paul Fletcher said commuter car parks reduced congestion on roads.
"There is a very sensible policy reason for this program," he told parliament on Tuesday.
A number of projects have been confirmed and completed since the auditor's report.
