Former minister of state at the Department of the Environment Fergus O'Dowd has said Irish Water has "abjectly failed" in its approach to introducing water charges.
Mr O'Dowd helped establish Irish Water during his time at the department.
In an article in the Irish Independent, Mr O'Dowd said the company has come across as arrogant, uncaring and had become adept at shooting itself in the foot.
Mr O'Dowd said that one of his key concerns had been that it did not become another "cosseted quango with a bonus culture".
Sadly, he said, the opposite had happened.
He described the disclosure in January that bonuses were to be paid at the company as one of the most jarring developments for him.
Mr O'Dowd said Irish Water should show its solidarity with customers and strangle its bonus culture at birth rather than allow it to flourish.
He recalled that he warned the department that Irish Water would be an unmitigated disaster if there was not enough engagement with the public.
He said that has proven to be the case.
Mr O'Dowd, a Fine Gael backbencher, lost his junior ministry in the Cabinet reshuffle during the summer.
Reacting to Mr O'Dowd's comments, the Taoiseach said that he does not agree that Irish Water is an unmitigated disaster.
Replying to Fianna Fáil's Micheál Martin during Leaders' Questions, Mr Kenny said that he does agree Irish Water has had teething problems.
The Taoiseach said that while there were issues with communication, Irish Water is here to stay.
In reply to claims by Mr Martin that water bills will be excessive, the Taoiseach said that 80% of all bills will be less than €24 per month, adding that charges will be capped for people with particular medical ailments.
Minister for a Foreign Affairs Charlie Flanagan said he thought there was a need for Irish Water to be more customer-friendly.
He said the company needed to engage with the public in a way that perhaps it had not to date.
Minister for Public Expenditure and Reform Brendan Howlin said it was not true to say that Irish Water is a disaster.
However, he said that everyone realises that it did not have a wonderful start and that it needs to reconnect with ordinary people.
Fianna Fáil's Barry Cowen has said it is not too late to bring in new legislation to "rectify the wrongs that have been done" in terms of Irish Water.
Speaking on RTÉ's Today with Seán O'Rourke, Mr Cowen said a lack of scrutiny and debate led to deficiencies.
He said: "I have no issue whatsoever with the concept of charging for that service. What I have issue with is the way in which the Government has gone about it, the way in which the Government has set up Irish Water and the costs associated with it, the rush to charge."
A spokesperson for Irish Water has said that the company acknowledges but disagrees with the comments made by Mr O'Dowd.
Speaking on RTÉ's Today with Sean O'Rourke, Elizabeth Arnett urged consumers to register and pay their bills, adding that as a utility company, it has the option of pursuing debt.
Ms Arnett also disputed claims that workers qualify for bonuses.
She said employees of the company avail of a performance-related award scheme, adding that no awards have yet been paid.
Ms Arnett said: "The process that we are in at the moment, as you know Irish Water was established at the start of this year, and annual performance targets are set both for the company and for individuals and so there hasn't been any payments made in relation to this, but it will be looked at in the context of the performance of the company for the year."