The controversial Renewable Heating Initiative (RHI) will cost Northern Ireland taxpayers an estimated £30m before the end of the current financial year at the end of March.
Finance Minister Mairtin O'Muilleoir was speaking at Stormont on Monday as he held talks with the main political parties about Economy Minister Simon Hamilton's plan to recover costs.
Mr O'Muilleoir said: "There are deep flaws in the proposal being put in front of us.
"In particular the real concern is that, while it was thought the new plan, the interim solution, would kick in on April 1, now we are being told that the state aid isn't available from the EU Commission - so it won't kick in at that time.
"So it (RHI) will cost us £30m this financial year."
He added: "I would rather be discussing a 19-year plan to save £500m - but that isn't on the agenda."