SINN Féin has called for the Renewable Heat Incentive (RHI) to be shut down.
In its response to a consultation on the future of the botched scheme, the party says it should be closed down next year, with claimants who are found not to have abused its generous terms to be reimbursed any outstanding capital costs.
However, Sinn Féin also argues that money paid to those shown to have exploited the scheme should be clawed back.
Closing down the RHI with a one-off payment to claimants was one of the options floated by the Department for the Economy when it launched the 12-week consultation on the scheme's future in June.
The consultation is due to close next Thursday September 6.
The scheme, which is the subject of a public inquiry due to resume next week, was launched in 2012 when DUP leader Arlene Foster was minister for enterprise, trade and investment.
Unveiling Sinn Féin's response yesterday, Newry and Armagh MLA Conor Murphy said RHI was not a good scheme that went wrong but a "bad scheme which was made even worse".
"We are now aware that a report commissioned before it was set up showed RHI was more expensive, less effective in promoting renewable heat, and higher risk than an alternative scheme.".
He said the scheme had "serious design flaws", including tariffs that were more lucrative for smaller, less energy-efficient boilers.
"Spending more public money on a scheme that is at best ineffective and at worse counterproductive to carbon reduction is unjustifiable," he said.
Mr Murphy called for the creation of a renewable energy scheme that reduced carbon emissions and combatted climate change.
