It has emerged that the costs of setting up Irish Water are almost twice the average of similar entities in England and Wales.
The company is defending the costs, saying the UK companies have existed for 25 years, and have become efficient over that time.
In a statement, Irish Water says the system here has suffered from decades of under investment and it will take time to catch up with our UK counterparts.
It is estimated Irish Water will cost around €180m to set up.
Sinn Féin's Environment spokesperson, Brian Stanley, says taxpayers are funding a corporate monster.
Mr Stanley said: "The Irish Government have created what I would call a 'corporate monster'. They have put it onto the backs of the local authorities who are already doing the job.
"They've created a call centre that employs a whole range of staff, they are paying themselves in excess of €100,000 in the case of senior managers and senior executives in Irish Water.
"The public are picking up the bill for it, and it should be done by reformed local authorities."