Civil servants tried to suspend a renewable energy scheme after the monthly payments to claimants increased almost six-fold in a year - from £264,000 to £1.5m by June 2015 - a public inquiry heard yesterday.
The Renewable Heat Incentive (RHI) ran into controversy over claims that it paid users a subsidy greater than the cost of the fuel used, leading to it being dubbed the 'cash for ash' scheme.
Officials from the former Department of Enterprise, Trade and Investment (Deti) had asked administrator Ofgem to "queue" new applications while they worked out the budget position.
The revelation came during evidence given to the inquiry yesterday by Gareth John, who was Ofgem's associate director for the non-domestic RHI from 2014.
He detailed how Ofgem was worried that the bill for its work might not get paid and also had concerns it had commitments to scheme applicants and might end up getting sued.
The request from Deti to pause the applications came when its monthly payments to scheme claimants rocketed up from £264,000 in March 2014 to £1.5m in June 2015.
Deti set up the botched energy scheme in 2012, with energy regulator Ofgem tasked with running it.
Mr John also told the inquiry that Stormont officials were repeatedly reminded about the issue of RHI cost controls, but claimed they appeared more interested in getting more people into the scheme. He said he had met Deti officials in Belfast in April 2014 and had discussed "the implementation of cost controls".
In Mr John's written evidence, he detailed the key difficulties he had with the RHI scheme in Northern Ireland, which included budget management and a lack of cost controls, and the increased applications in the lead up to suspension of the scheme.
"In my view, one of the problems with the scheme was Deti's failure to undertake proper budget analysis for the scheme. This was the responsibility of Deti as the party responsible for setting the tariff structure, reviewing policy and managing the budget," he submitted.
A public inquiry was set up last year to investigate what happened in the ill-fated scheme.
Today, another Ofgem official, Edmund Ward, is set to give evidence.