A former Stormont minister appeared emotional as he claimed he was "just one boy" against multiple attempts to "smear" him.
Jonathan Bell claimed the DUP "fitted" him up, the Executive Office briefed against him and a journalist advised the DUP how to discredit him.
"I fear I have been the victim of a massive smear campaign," he said.
Mr Bell made the claims while giving evidence to a public inquiry in Belfast into how costs for a green energy scheme spiralled.
He was minister at the Enterprise Department which oversaw the publicly funded Renewable Heat Incentive (RHI) scheme.
Mr Bell was suspended by the DUP in December 2016 after giving an interview to BBC journalist Stephen Nolan about the RHI scheme.
He has made explosive claims that DUP special advisers were reluctant to introduce cost control tariffs to the scheme.
Appearing at the RHI inquiry on Thursday, Mr Bell claimed the DUP has "fitted" him up.
Text messages between Mr Bell's special adviser Timothy Cairns and DUP leader Arlene Foster as well as another special adviser Timothy Johnston reveal that he (Mr Cairns) would "fit his story to whatever the party narrative was to be", Mr Bell claimed.
Mr Bell also told the inquiry of attempts to "smear him".
He has claimed that an Executive Office official described him as a "monster who had to be put to sleep" and that a journalist gave the DUP advice on how to discredit him.
Mr Bell said that advice from the journalist included attacking his Christian faith.
"I have to say to you, I am just one boy, I can't operate against the Executive Office," he told the inquiry.
Mr Bell also claimed that the DUP offered a newspaper an exclusive story about him being a bully, if they used the headline "Bully boy Bell".
"I fear I have been the victim of a massive smear campaign, and I fear this is part of the smear campaign," he said.