Eighteen religious orders are collectively contributing about 12% of what was the expected cost of the claims but the final bill for the abuse scandal is expected to rise after the High Court ruled earlier this week that the eligibility criteria for applicants to the fund was too restrictive.

The court said the age limit for applicants should be raised from 18 to 21 years to take account of young women who were sent to mother-and-baby homes after the age of 18. It is believed the ruling could result in a fresh round of applications to the Residential Institutions Redress Board (RIRB), which administers the compensation scheme.

That would push the end cost above the most recent estimate of €1.1 billion and reduce the proportion covered by the religious orders.

The 18 orders struck a deal with the State to give €128 million to the fund through a combination of cash, property and counselling services. The deal will not be reviewed.

Fine Gael’s education spokesman, Brian Hayes, criticised the Government’s handling of the deal, saying: “It was probably one of the most reckless, incompetent and financially illiterate deals that was ever struck.”

A spokesman for the Department of Education, which set up the RIRB, said there was no question of the deal being renegotiated and the Christian Brothers, one of the orders involved, also said the issue would not be revisited.

Spokesman Br Edmund Garvey said: “The religious congregations said they were making a voluntary contribution and that was accepted by the State. It hasn’t been raised with us since and there is no suggestion it will be.”

The Department of Education spokesman said no decision had been taken yet on whether the High Court ruling would be appealed to the Supreme Court or if the legislation setting out the application criteria operated by the RIRB would be amended.