The chairman of the Public Accounts Committee, John McGuinness, has launched a blistering attack on Irish Water, saying its boss John Tierney "is the wrong man" to lead the organisation.
In an interview with the Sunday Independent, Mr McGuinness also says Fianna Fail "must get 45 seats" or the future of the party, as well as leader Micheal Martin, will "be in question".
He has also said he has been "vilified" within his own party for speaking out.
Mr McGuinness opposed the establishment of Irish Water and has called for its abolition, but he has also accused former environment minister Phil Hogan of "doing more damage than Cromwell".
Mr McGuinness said it was a "daft idea" by the Government to establish the "super quango" without proper planning and political proofing, but has called on Mr Tierney to depart from his post.
"I know him personally from his time on Kilkenny council. I think he is the wrong man for that job, in terms of the size of the operation. What effort was made to get the skill set required to run a company like that? It was not his fault, the Government set it up, but it is now, as he took the job and is in charge," Mr McGuinness said.
In relation to Mr Hogan, who was a constituency rival of Mr McGuinness in Carlow-Kilkenny until he became EU Commissioner last year, the PAC chairman was scathing in his criticism.
"He is my constituency colleague but he had a job to do, and he botched the job of establishing Irish Water. Like everything else, they are reluctant to do a U-turn when a mistake is made," he said.
"But a big mistake was made; they should have gone back to the drawing board. It wasn't politically proofed and introducing it at a time when the country and its people were in such dire straits was crazy."
He also has railed against the huge cost borne to establish Irish Water.
"It was a daft idea to bring about this super quango when this Government promised it would abolish quangos. That has not happened. Yes, there will be problems in turning back the clock on Irish Water, but the costs of doing that would have to be considered in the context of keeping the thing going," he said.
"What country in the world would transfer €11.5bn in assets to, essentially, a private company and then pay that company €500m a year out of road tax. Nobody seems to be bothered that this money was raised out of road tax, and the roads in the counties are falling asunder."
On Mr Hogan, Mr McGuinness said 'Big Phil's' impact on their home city of Kilkenny had been disastrous, particularly his abolition of town councils.
"All you have to do is look at this city and see the legacy of Phil Hogan. He has divided our city in two. He has ruined and wrecked the structures of local government. He did more damage to it than Cromwell did when he was here," he said.
Speaking as the controversy over the conservation grant raged, Mr McGuinness said it should not be paid, it was as simple as that. It was being given to people who were not co-operating; it was a nonsense that should be stopped, he added.
Turning to the pending general election, Mr McGuinness said Fianna Fail must return with at least 45 seats or the future of the party, as well as leader Micheal Martin, was in question.
"Looking to the general election, we have to come in the mid-40s in terms of seats. It is an issue for Micheal Martin and the party," he said.
"Based on the results in the by-election here and the local elections last year, you would imagine we should be targeting the mid-40s in terms of seats.
"If you were to take the current polls, we are going to come in in the mid-30s. That would be very disappointing for the party."
In terms of coalition options, Mr McGuinness said Fianna Fail could not afford to close the door on any partner at this stage.
"If Fianna Fail gets the numbers to be a player at the table to form a government, they have to keep all of their options open. Yeah, maybe we will look at Sinn Fein, yeah we will look at Fine Gael, yes maybe we will have this arrangement of supporting a minority Fine Gael government from the opposition benches," he said.
But the PAC chairman, who has clashed with his party colleagues over his outspoken views, said the party still had not laid the ghosts of "that defeat of the 2011 election" to rest.
"I am often accused of speaking in a negative vein about everything and anything. If you don't expose the negatives, you will forever have them as ghosts in the room," he said.
"Therefore, these negatives have to be dealt with and they haven't been dealt with.
"It is like a bereavement, and we certainly had a bereavement in 2011. Fifty-eight seats, 58 of my colleagues did not come back."
He went on to talk about how he has met strong resistance to his outspoken views.
"Within my own party, Fianna Fail, I am vilified for talking about radical reform and renewal outside the parliamentary party room, because inside it nothing is ever discussed at length, and any attempt to introduce meaningful discussion or debate is met with a horrified silence.
"My first duty is to the people, not the party, and if my party will not listen, I will take my concerns to the people," he said.
Mr McGuinness said the party was still operating under the same culture that led to those 58 seats being lost.
"But what has not happened within the party is that culture which lost us 58 seats, that culture is still there. A culture of secrecy, interference from the party at national level in local affairs, the non-examination of why people have left the party, why really did Averil Power leave? Why really did David McGuinness leave?" he said.
"The dumping on individuals because they leave and the attempts to discredit them is part of that old culture within Fianna Fail. Shooting the messenger, playing the man not the ball.
"We have never dealt with those cultural issues since that defeat in 2011. No, we haven't dealt with the reasons why we lost so many seats.
"There is a lot of disquiet about it."