SDLP leader Colum Eastwood has threatened legal action after a Sinn Fein MLA linked the party to "potential criminal or political negligence".
Speaking on BBC Radio Ulster yesterday morning, Declan Kearney hit out at the SDLP and Ulster Unionists for voting last year in favour of keeping the Renewable Heat Incentive (RHI) scheme open.
"Sinn Féin voted to close it down. Maybe we should have a public inquiry and maybe there would be a great deal of public interest into whether there has been potential criminal or political negligence on the part of the SDLP and UUP," he said.
At the time the SDLP's Claire Hanna laughed off the remarks as "spin", saying the party had voted to keep open an amended scheme with cost controls.
But later on Radio Ulster's Talkback programme, Mr Eastwood called for the remarks to be withdrawn.
Speaking before the Sinn Féin finance minster announced a public inquiry, he said: "I don't understand why Sinn Féin for example aren't backing this call [for a public inquiry]. Instead they are making scurrilous claims.
"Some people can say things like criminal negligence but if they don't withdraw them, they are going to find themselves facing very difficult issues in the coming days."
He added: "I am absolutely threatening legal action, because if people want to throw around words like 'criminal negligence'... they should stand over that or they should withdraw it or they will find themselves receiving legal letters."
Ulster Unionist leader Mike Nesbitt also hit out at Sinn Féin, saying: "It shows how desperate they are to save face that Declan Kearney would make such an outrageous and ridiculous claim.”
Sinn Féin yesterday did not respond to requests for a comment.
