The State denied up to 12,000 vulnerable people their disability allowance payments, RTÉ Investigates has learned.
And if those vulnerable citizens sued the State for the payments, the legal advice was that their cases were likely to succeed.
A secret memo prepared for the Cabinet in 2009 reveals that the State was told it could be facing up to €700 million in claims for maintenance payments from people with disabilities.
The memo, which was obtained by RTÉ Investigates, also advised the State against conducting a trawl of HSE records to determine how many people were affected. It said that such an exercise would likely garner media attention and "could generate further claims which otherwise would not have been made".
Regulations were introduced in the 1980s to stop the payment of maintenance allowances to those in residential care.
In late 2008 the State settled for €60,000 a case taken on behalf of a woman whose maintenance allowance ceased when she was admitted to a psychiatric facility in 1983.
The legal view given to the State at the time of the case was that the regulations were unconstitutional and stood little chance of surviving legal challenge.
The allowance was worth €50 per week in 1983 and rose to €80 per week in 1996.
The case was taken on behalf of the woman in the wake of the 2005 Travers report, which uncovered three decades of a regime of illegal nursing home charges.
Legal submissions on behalf of the woman used the exact same language as cases taken in the nursing home scandal, noting that the regulations used to stop the disability allowance payments were ultra vires which in effect meant that they were void and of no legal effect.
Despite this, the practice of denying Disability Allowance payments to those in institutional care continued for many years and affected thousands of people in up to 140 institutional care homes, most with profound disabilities.
The secret memo, which was prepared for Cabinet in the wake of the woman's case, said that the advice of the Attorney General's office was that "the State was extremely unlikely to be able to defend this case".
It also noted that, while the €60,000 payout was not itself significant, the number of potential other cases were.
The memo said that somewhere between 4,000 and 10,000 people could be impacted during the time the payments were made by the Department of Health and said there were a further 2,700 people impacted after it switched to the Department of Social and Family Affairs.
It estimated that claims against both departments could be somewhere between €350m and €700m, before legal costs.
At the time, the State did not know exactly how many people were impacted. But the memo noted that a "comprehensive trawl" could be done on "HSE administrative records, covering a 30-year period" for more than 140 different institutional care centres.
But the memo advised against this.
It stated: "Such an exercise would be unlikely to escape media attention or speculation and could generate further claims which otherwise would not have been made". It said that the then-minister did not consider this course of action appropriate.
While the State was hoping to avoid further legal cases, RTÉ Investigates is aware of at least one other case that followed.
It was taken on similar terms and was settled quietly, in line with the confidential government strategy.
There were a handful of parliamentary questions on behalf of people and one request for information. But other cases did not emerge.
Several experts told RTÉ Investigates that many of those likely to have been affected would not have been aware of the case, either because they were in sheltered environments, or may not have had the capacity to understand or initiate their claim.
They would have been on relying on the State to care for them and advocate for them.
The Cabinet memo also spoke about a contingency plan – to set up a statutory repayments scheme, but this, it said, was not to be triggered unless cases started coming in.
In a statement to RTÉ Investigates, the Department of Health noted that the allowance, known as the Disabled Persons' Maintenance Allowance (DPMA) between 1973 and 1996, was paid to people "over 16 years of age where neither the person nor the person’s spouse was able to provide for themselves".
It went on: "However, people with a disability who were resident in long term care facilities did not receive the DPMA after the first 8 weeks in residential care. There have been a very small number of closed historic cases where individuals challenged the withdrawal of this allowance."
It also noted that, in 1996, the responsibility for the payment was transferred to the then-Department of Social and Family Affairs, when it was renamed the Disability Allowance.
Earlier this week, the Mail on Sunday reported on documents supplied by Department of Health whistleblower Shane Corr. They revealed the nature of a legal strategy to limit exposure to claims made on behalf of people in certain nursing homes.
