The chief executive of Ervia, the parent company of Irish Water, has said the controversial utility may not exist after the next general election.
Speaking at the MacGill Summer School in Donegal, Michael McNicholas also conceded that the company will not be able to survive without public support.
"We have been very clear that we cannot deliver on the previous plans that were put forward. They are too expensive in our view and we can't deliver what has been promised in the time scale," he said.
He then cast doubt on the future of Irish Water.
"We have put forward a realistic engineering plan that we believe will address these issues sensibly, economically and in a time frame that is acceptable, and we are very committed to delivering this plan; that is provided we are still around after the next election, I should say," Mr McNicholas said.
"For Irish Water to work it must have political and public support, and it is clear that some sections of the public remain sceptical about it and some of the political voices in Ireland are totally dismissive of it."
His comments, aired on RTE's Morning Ireland, come shortly after Irish Water, which is headed by former Dublin City Manager John Tierney but which answers to Ervia, was brought back into the spotlight when it was revealed that less than half of the people eligible had paid their first quarterly water bill.
Mr McNicholas launched a staunch defence last night of the beleaguered company.
"I believe it's the right model, we've made a lot of progress in 12 months," he said.
"Yes, we've made mistakes; yes, we've a long way to go; but there isn't a single utility company set up in this country that wasn't pilloried at the start.
"Frankly, no government has ever spent enough money on water infrastructure and it's rubbish to say that in the last 10 years we were spending enough. We're racing to catch up with European directives because our wastewater's in such a disgraceful position."
He added that Irish Water "came up short" when it came to selling the introduction of water charges to the public.
"It could have been clearer about just how unfit for purpose the current water infrastructure is and just how much work was required to give us an infrastructure that is needed for a modern economy," he said.
"The reality is that we have not been investing efficiently or sufficiently in our water services. So when people say introducing water charges means we are paying twice, the reality is we have not even been paying once.
"We need more investment as a matter of urgency, and this additional investment has to be paid for in some shape or form by society and by business."
Mr McNicholas was speaking during a panel discussion on the setting-up of Irish Water, alongside Green Party leader Eamon Ryan, Sinn Fein's Pearse Doherty and Fianna Fail TD Barry Cowen.
Environment Minister Alan Kelly was due to take part but withdrew due to a diary clash with a meeting in Luxembourg.
The company and the Coalition were sharply criticised by the Sinn Fein and Fianna Fail TDs, with Mr Cowen calling for the abolition of Irish Water.
"It has failed and it should go before it does any more damage. It's time to call a stop to the absurdity of the Government losing money on a charge," he said.
An anti-water charges protest will take place in Glenties on Friday when Taoiseach Enda Kenny is due to speak at the summer school.