DUP MLA Jonathan Bell vowed to tell the truth over the Renewable Heating Incentive scandal, saying it will ruin his political career.
The Strangford MLA appeared in a BBC One Nolan Investigation interview on Thursday night.
In a preview, the former Enterprise Minister said he was doing his duty in a tearful interview: "I did not seek office to close hospitals while hundreds of millions of pounds are abused. I'll tell the truth and my political career will be ruined."
"I have had to do one of most difficult things in my life; tell the Northern Ireland public the truth and shine a light and deal with a major problem.
"Dr Paisley was right 'tell the truth should the heavens fall, so do with me as they will'.
"The facts are documents, emails, times and dates. You will not find one single thing that is not the truth. I have done my duty.
"So I have told the truth and I believe God does not punish people for telling the truth.
"I'm a very poor Christian, but I've a great God."
He added: "Let's see how it plays out."
The interview centres around the Renewable Heating Incentive, which will cost the public hundreds of millions of pounds in overspent funds auditors warned after it was exploited.
It has been described as the biggest scandal in the history of devolved government. Pressure has been mounting on First Minister Arlene Foster.She was the minister that introduced the policy and has faced down calls to resign.
Her successor in the Department of Enterprise Trade and Investment Jonathan Bell eventually closed the scheme.
On Wednesday Stephen Nolan Show revealed that Mrs Foster had a "heated conversation" with her DUP colleague Jonathan Bell, over his plans to end the scheme.
Speaking on his Radio Ulster Show, Stephen Nolan explained why the interview was held off for television on Thursday night.
"I want the public to see the whites of his eyes," he said.
The full interview will be broadcast on BBC One at 10.40pm.
Having thought since Spotlight that Mrs Foster would survive, I'm increasingly of the view that her position may soon be untenable.— Alex.Kane (@AlexKane221b) December 15, 2016
The Renewable Heating Incentive was supposed to help businesses mitigate the costs of running eco-friendly boilers actually ended up paying out more than the cost of the fuel - so the more people burned, the more public money they earned. Some applicants were found to heat buildings on an industrial scale just to make money.
Unlike a similar scheme in Britain, no cap was initially put on the payments.
It has been revealed that after civil servants urged for the closure of the scheme in June 2015 until a tiered system was introduced in November, there was a spike in applications.
November 2012 - Arlene Foster, then Enterprise Minister, announces the Renewable Heat Incentive scheme for businesses.
October 2013 - A whistleblower emails Mrs Foster to express concerns over the scheme.
Autumn 2013 - The woman is referred by Mrs Foster to officials from her Department of Enterprise, Trade and Investment, and she urges them to address the problems.
May 2014 - The whistleblower emails again, after the civil servants appear to do nothing. She explicitly outlines how the scheme was being abused, was paying out exorbitant sums of money, and could not be ignored any longer.
December 2014 - The scheme is extended to domestic customers by Mrs Foster.
November 2015 - With the realisation the funding available for applicants is uncapped, Stormont tightens the rules.
But a massive late surge of 900 applications is received before changes can be made.
January 2016 - Another whistleblower civil servant tells the Executive the scheme is being abused.
February 6 - New Enterprise Minister Jonathan Bell (above) makes a shock announcement that the RHI scheme to be scrapped.
February 9 - Michael Doran of Action Renewables warns it will force renewables from "boom to bust."
June - Auditors begin investigating concerns.
July 5 - A damning Audit Office report states a farmer will make £1m of government money just for heating an empty shed. It reveals that more than £1 billion of public money will be paid to Northern Ireland-based businesses by 2036 after they installed new appliances under the RHI scheme.
October - Stormont's Public Accounts Committee (PAC) call the mishandling of the RHI scheme "one of the biggest scandals" since devolution. SDLP Assembly member Daniel McCrossan tells officials from government utility regulator OFGEM, which administered the scheme: "It was very clear the department was asleep at the wheel but I am horrified that you too were asleep at the wheel in relation to this."
November - The Public Accounts Committee is told that a £405m hole will have to be plugged over the 20-year lifetime of the RHI.
Dr Andrew McCormick (above), permanent secretary for the Economy Department, says he can't think of any government scheme being worse value for money.
12 December: First Minister Arlene Foster says she won't quit over the fiasco following allegations that she did not act appropriately when concerns were first raised about the scheme. It also emerges the brother of a DUP special advisor and a Ferrari showroom have benefited from the error-ridden scheme.
13 December: UUP leader Mike Nesbitt claims to have uncovered the "smoking gun" of Arlene Foster's involvement in the decision-making process in connection with the flawed RHI scheme.
14 December: The SDLP says it will table a motion of no confidence to exclude Arlene Foster as First Minister. Sinn Fein says it won't back the motion. Meanwhile the UUP says the UK Government can no longer ignore the "national scandal".
The DUP's Nigel Dodds hits out at a "scurrilous attempt" to blame Arlene Foster for the botched energy scheme. The party releases what it says is a copy of the 2013 email sent from the whistleblower to Mrs Foster, saying that it raised no specific concerns about RHI.
15 December: Arlene Foster says she has nothing to hide from a BBC interview with former DUP minister Jonathan Bell, who vowed to tell the truth about the scandal, adding the revelations will end his political career.
Jonathan Bell claims DUP advisers attempted to delay the closure of the scheme in its original and generous format. He also said attempts were made to remove references to the Finance Department and Arlene Foster in records. The claims were denied.
19 December: Arlene Foster is to make a "full statement" to MLAs as the devolved assembly is recalled for a special setting to discuss the growing political crisis in the run-up to Christmas.