Irish Water has been criticised for failing to produce any records to support its claim that abolishing the utility would cost €100 million.
Freedom of Information documents released to Sinn Féin TD Pearse Doherty confirm the figure, which came in the wake of the general election, is an estimate given verbally to the media.
Mr Doherty said the correspondence proved there was no basis to the utility’s “back of the envelope calculation” of the costs.
"This was an exercise in self-preservation by them and the least we would expect from Irish Water, " the Donegal TD said.
“They have no email, no documents to underpin the €100 million figure.
“This was an attempt to try to scare the public away from parties who suggested that Irish Water should be abolished.”
An Irish Water spokeswoman said it had been made clear at all times that this was an estimate.
Mr Doherty had sought all “minutes, records, correspondence etc, related to the cost of charges and of abolishing Irish Water since March 1st, 2015”.
In response, the company provided a number of documents including a briefing note prepared by the parent company of Irish Water, Ervia, the Irish Water business plan and a review by the Commission for Energy Regulation.
The utility said it was asked by journalists about the “likely ‘cash wind-up costs’ of Irish Water including payroll, contracts and leases, IT systems and services”.
“An informed estimate of €100 million was given verbally but it was made explicitly clear that this was a broad estimate only and would need to be fully costed in the event that the winding up of the utility actually came about,” it said.
Mr Doherty said Irish Water had “plucked the figure from the air” and had engaged in political lobbying without any basis.
The TD added: “Politicians have been asking Irish Water for figures in relation to payment of bills and they won’t give it to us so we have to go to Freedom of Information which arrives long after the information should be released.
“Yet when it comes to a question from a journalist about how much abolishing Irish Water would cost, they pluck a figure from the air.”
Figures later released by the Department of the Environment said abolishing the utility would cost between €85 million and €169 million.
In the documents released to Mr Doherty, Ervia warned abolishing water charges was in breach of the European water directive.
It also claimed the establishment of a single national utility was the “single biggest transformation of public services in the history of the State”.