A senior DUP politician has claimed "nobody" spotted the "fatal flaw" in the Renewable Heat Incentive scheme, despite six warnings before its closure.
East Antrim MP Sammy Wilson made an impassioned defence of First Minister Arlene Foster yesterday, even claiming she has "gone up in people's estimations".
"The RHI scheme had many hands on it, not just Arlene's, and nobody spotted the fatal flaw which cost this money. Secondly Arlene, once it became known has taken hold of the problem and has been looking at how to resolve the problem, that's the mark of a true leader," he said.
Interviewed on BBC Radio Ulster's Nolan Show, Mr Wilson also claimed that subsidy tariffs in Northern Ireland were lower than in Britain, meaning there was no requirement for 'tiering' to control pay-outs over time.
"The argument was we're actually giving a lower tariff than the rest of the United Kingdom so therefore we don't need to tier it," he said.
Up until 2015 the Northern Ireland version of the UK green energy scheme operated with just one tariff of 5.9p/kw. It then rose to 6.4 pence.
The two tariffs in Britain halved over the same period.
This meant returns were much higher for applicants in Northern Ireland, especially since 2015.
According an audit report, the annual Northern Ireland RHI grant for a typical boiler installed in May 2015 could have been almost twice as much for the same boiler in Britain.
SDLP Mid-Ulster MLA Patsy McGlone claimed Mr Wilson was "woefully muddled".
"The fact that Sammy was himself finance minister for the development and implementation of RHI and still has no grasp of the detail is nothing short of shambolic," he said.
"His claim that once Arlene Foster discovered the problem that she took hold of it and sought a resolution is laughable. It is clear that recouping public money only became a priority for her once people started calling for her job."
The Irish News has previously reported a total of six missed warnings about flaws in the development of the scheme before its closure in February 2016.
In September 2011, more than a year before its launch, 13 companies and other bodies responded to a consultation detailing concerns about "over-incentivisation".
Green energy consortium Biomass Energy Northern Ireland (BENI) warned that claimants could use multiple small boilers to make more money, while leading energy firm Airtricity said the scheme must be closely monitored to ensure "perverse incentives to over-generate can be avoided".
In early September 2013 a whistleblower emailed Arlene Foster raising her concerns about the scheme being abused and the following month, BENI responded to a second Deti consultation repeating its concerns.
In May 2014 the original whistleblower sent a follow-up email repeating concerns, while in autumn 2015 then Deti minister Jonathan Bell alleged that DUP advisers delayed his plans to close the scheme, claims denied by the party.
In January 2016, a second whistleblower contacted Mrs Foster - now First Minister - claiming that a farm shed and factories with large boilers were running heat 24 hours a day just to make money.
