The federal government's botched Green Loans program was a magnet for every "shark and shonk" in Australia and the department that oversaw the scheme agrees there were "difficulties".
The $300 million program to fund measures such as solar panels for homes and low energy lighting was curtailed by the government in February following claims of mismanagement.
Department of Climate Change and Energy Efficiency deputy secretary Malcolm Thompson admits there were delays in paying assessors and delivery of sustainability assessment reports to households, as well as problems with booking assessments.
"We acknowledge the difficulties experienced in the delivery of the program," he told a Senate inquiry into the program sitting in Sydney on Tuesday.
"We have not tried to hide those."
A former assessor with Green Loan Assessors Co-operative Pty Limited (GLACO), Leanne McIntosh, told the inquiry there were no checks and balances.
"When there were no checks and balances in place you attract every shark and shonk in Australia - putting out a welcome mat to 'come rip us off'," said Ms McIntosh, who is representing a group of 58 GLACO assessors.
Under the scheme, householders were offered free energy efficiency audits by trained assessors, vouchers to spend on green products and access to interest-free loans of up to $10,000 to improve energy efficiency.
Mr Thompson said the design of the program combined with strong demand had created challenges and that the department was working to clear a backlog of home sustainability reports.
Ms McIntosh was scathing of the government's overall handling of the scheme, saying the resulting confusion "caused a massive loss of faith".
She said it failed to live up to promises of a national marketing campaign, an efficient email and assessment booking system and other measures to implement the scheme.
Assessors across Australia who were conducting assessments on behalf of the government through GLACO say they are owed up to $500,000 in fees due to mismanagement and poor administration procedures under the scheme, according to Ms McIntosh's submission.
Assessors have previously complained about delays in receiving payment but the government has said part of the problem was invoices with incorrect information.
Mr Thompson said that currently invoices were being paid within the 30-day timeframe.
Ms McIntosh said she was attracted to the scheme because potential assessors were told if they invested $4000 in training, insurance and accreditation they could effectively buy themselves a job for four years.
"We all invested our money and time on that basis in good faith," she said.
"What we got was a dysfunctional program that has caused us loss of income and untold stress."
Mr Thompson said since February, steps had been taken to make the remaining features of the program more orderly.
The government had introduced caps to the number of assessors contracted, and the number of bookings and assessments that could be taken in a week.
Asked by the Senate committee whether the introduction of caps at the outset of the program would have made it more sustainable, Mr Thompson said: "I don't know. That is speculation."