It will take at least another year before Irish Water can get a true sense of how many households will pay water charges, according to the chief executive of Ervia, Irish Water’s parent company.

Michael McNicholas said it was “far too early” to draw conclusions based on recent figures which showed Irish Water had collected less than half of all domestic water charge payments due to it for the first three months of billing.

He said the company had issued households with just one bill to date, and it would take at least a year to get “a good sense of where our revenue model will be.” He added: “We’re only starting.”

Groups opposed to domestic water charges claimed the 46 per cent payment rate vindicated their campaign to have the charges scrapped, though Minister for the Environment Alan Kelly said the figures was "an encouraging start to a long-term project."

Mr McNicholas defended the establishment of Irish Water and said he was confident it would survive the next general election. “This country needs a national [WATER]utility. It has a national utility. It will have a national utility after the election because there is no other rational solution,” he said on RTÉ’s This Week programme on Sunday.

Mr McNicholas said Ireland did not have fit-for-purpose water infrastructure. Some 50 per cent of treated water was lost to leakage, shortages had been recorded in three of the past four years and there were 44 urban centres where raw sewage was being discharged into rivers and the sea.

“In 18 months the new national utility has done more to address our infrastructure than has been done in decades,” he said. Irish Water would invest €400 million into water infrastructure this year and expected that figure to rise to €800 million by 2018, he added.

The utility is in ongoing talks with trade unions at the Labour Relations Commission over unpaid staff bonuses. The payments were introduced as part of a new pay model at Ervia in 2013 and Irish Water inherited that scheme when it was set up. Under the arrangement, 50 staff members were in line for a 2.75 per cent bonus, 165 for a 6.5 per cent payout, 65 were expecting a 14 per cent bonus and the top 29 were set to get a 15 per cent bonus on top of their salaries.

Mr McNicholas insisted the payments were not bonuses but rather were part of a “performance-based system”. Nevertheless, in light of negative media coverage and attention last year, the company decided not to make the payments. He said the portrayal of the payments as bonuses was “incorrect, unfair to staff” and damaged trust in the company.

He also defended his own salary of €250,000, saying it was fixed by Government and was in line with public pay policy.