Prime Minister Scott Morrison has been accused of playing a central role in an alleged car park rorting scandal ahead of the last federal election, totalling nearly $700 million.
A Labor-majority senate committee has found Mr Morrison and then-infrastructure minister Alan Tudge were "central" in running the canvassing process, which would favour projects in Coalition-held and marginal seats.
Labor senator and committee chair Tim Ayres warned the commuter car park fund represented only one aspect of the larger $4.8 billion Urban Congestion Fund, which used the same flawed processes.
But Coalition senators said they were "disappointed" with the conclusions of the committee, adding Labor was "deliberately omitting key facts" showing it supported the program.
It comes nearly six months after the Australian National Audit Office's released a scathing 104-page report into the program, finding the process for choosing which proposals got funding was not "demonstrably merit-based".
A list containing the top marginal electorates in the country was created by staff within Mr Tudge's office, the audit office previously confirmed, but the report said evidence "strongly points" to Mr Morrison being aware of it also.
Mr Morrison was handed a two-week deadline by the opposition on Thursday evening to explain his involvement in the program and the creation of a "top 20 marginals list".
Mr Tudge has previously denied any knowledge of the list in question, while Mr Morrison has avoided directly answering the question.
But the report recommended Mr Morrison outline his involvement to parliament by December 17, along with the deputy prime minister and any other ministerial offices involved, in the decision-making process.
"This inquiry has reinforced that there is no effective enforcement mechanisms in place, for ensuring that public administration is aimed at addressing areas of most need in an impartial, ethical and efficient way," the report said.
"There is clearly a need to better hold the executive to account and ensure that any actions taken, or decisions made are in the best interests of the Australian public."
The ANAO report, released in June, showed more than three-quarters of commuter car park sites selected were in Coalition-held seats, with 64 per cent located in Melbourne.
Mr Tudge defended the UCF scheme at the time, saying the need for commuter car parks was most apparent in Melbourne.
But the ANAO report outlined there were greater levels of road congestion in Sydney and south-east Queensland.
"The ANAO found that 'the majority of the most congested roads in Australia' are located in Greater Sydney, and that 'the proportion of the 10 most congested roads that are located in South East Queensland is forecast to exceed Greater Melbourne in 2031," the committee report said.
It also said Mr Fletcher continually refused to hand over relevant documents to the Senate relating to the rorting allegations.
In the committee's response, it noted the misallocation of the funds reflected an endemic culture within the government of using public money for political purposes.
It also outlined it was "egregious" that a press release was considered enough documentation and authority to progress projects worth millions of dollars, without the need of proper departmental consideration.
The report also claims Treasurer Josh Frydenberg put forward four applications in his seat of Kooyong, with budgets attached and no cost analysis done on the proposed projects.
Coalition deputy chair Claire Chandler accused Labor of a double standard after it took a very similar urban infrastructure policy to the 2019 election.
The report made a number of "political criticisms and commentaries designed to undermine public confidence in the government's commuter car park investments", she said.
"Both sides made commitments to fund specific car park projects as well as a range of other infrastructure projects," her dissenting report said.
"Yet Labor's stance now seems to be that it was not appropriate for the Coalition to commit to car park projects on this basis, but perfectly acceptable for Labor to do so."
Senator Ayres and Labor's infrastructure spokesperson Catherine King said the report was more proof that Mr Morrison should introduce a federal integrity commission to restore public confidence in the funding and grants process.
"With $890 million unallocated in the Urban Congestion Fund ahead of the 2022 election, the committee has made a number of urgent recommendations to ensure that there can be public confidence in the allocation of those remaining funds," their joint statement said.
"Further recommendations would expand accountability and transparency in the use of taxpayer money, including the urgent establishment of a National Anti-corruption Commission.
"If the Prime Minister wants to keep running from scrutiny that's up to him, but he can't hide from the fact that he is up to his neck in this $4.8 billion scandal."