Social Democrats TD Gary Gannon says Simon Coveney's latest comments on the Katherine Zappone controversy "annihilated" the truth.
It comes after the Foreign Affairs Minister said Ms Zappone did not ask him for a Special Envoy role at the United Nations.
He earlier told an Oireachtas committee the creation of the new position was being explored by his department, before he asked Ms Zappone on March 3rd if it was something she would be interested in.
But he added he should have been clearer at the time it was not a job offer and acknowledged he "made mistakes" - including giving "sloppy" answers to the Oireachtas.
Deputy Gannon told The Hard Shoulder Mr Coveney's appearance created more questions than it answered.
"The minister apologised to us today for the misleading answers he gave us last week, and I think he's going to have to apologise again because his answers today didn't only stretch the truth, they absolutely annihilated it.
"He wanted us to believe today that Katherine Zappone was thanking him for a job that didn't exist, was asking him for a start date for a job she wasn't offered.
"The minister came in today to protect himself and, I think, make a little bit of a mug out of Katherine Zappone - and that was clearly what he tried to do today.
"I think today's contribution actually left more questions than last weeks.
"I was really disappointed in the minister's undermining even of the role of lobbying.
"He wanted us to believe that no lobbying took place - even again, the minister had time to reflect on this.
"[He] came into the committee today and tried to demonstrate the type of contrition that probably would have got him off the hook back in August - but at this stage he's just unraveled himself so much, he just kept digging, that he's just left more questions than what he answered".
Asked if he felt Mr Coveney's position is tenable, he says he would not support him.
"To my view, Simon Coveney has undermined his position substantially here.
"In the first instance, I'd like to hear what the Taoiseach has to say - I believe there's enough there today that Simon Coveney has to come into the Dáil, not the committee room, into the Dáil and answer further questions.
"But the Taoiseach has to demonstrate leadership here.
"I have no confidence in Simon Coveney following on from the misleading comments he's given to media and to our committee".
