More than 22,000 people will benefit if the Government decides not to apply the Statute of Limitations to certain categories of people who were illegally charged nursing home care.
Yesterday Ms Harney indicated the statute, which would bar compensation claims for charges prior to 1999, would be invoked in relation to deceased persons.
She said the Attorney General, Rory Brady, had advised that the Government may not be able to apply the statute in cases where the person was still alive, or to the estate of a deceased person who was of unsound mind.
Meanwhile it has emerged that all former ministers for health, including the former taoiseach Charles Haughey and the Minister for Finance Brian Cowen, will be invited to appear before the Oireachtas Health Committee, which is to hold a series of special hearings into the affair over the next couple of months.
Yesterday Ms Harney told the Dáil that the Health Service Executive had now provided estimates which indicate that the Government faces a bill of €532 million in relation to the illegal charges that were applied between 1999 and 2004.
The final cost could be much higher, she acknowledged, with outside estimates of up to €2 billion for all charges dating back to 1976, when the illegal charging began.
It is now estimated that 299,249 people are eligible for a refund for the period 1976-2004, although the majority are now deceased, and as such would be barred if the Statute of Limitations was applied in the way indicated by the Tánaiste yesterday.
The €532 million estimate did not include potential payments to people who are still alive, but who were in long-term nursing care prior to 1999, and would be entitled to compensation prior to 1999.
She said 22,000 people were in this category, half of whom were in mental health institutions.
The Tánaiste plans to bring definitive proposals to the Cabinet at their first meeting after Easter, which will take place on April 6th, about how the scheme will operate.
No final decision has been taken on the issue of the Statute, and there are ongoing discussions between the Attorney General and the Tánaiste on the matter.
Meetings of a special Cabinet sub-committee, including the Tánaiste, Taoiseach Bertie Ahern and the Minister for Finance, would also be taking place to finalise the proposals.
There have been nearly 12,000 inquiries to a special help-line, and repayment scheme office, established to deal with the issue.
Meanwhile the Oireachtas Committee on Health is to finalise its terms of reference for a planned inquiry into the overcharging affair.
It is expected that committee chairman John Moloney and his colleagues will outline plans today for a series of special hearings into the affair over the next two months.
Mr John Travers, the author of the report on the nursing home charges, is expected to be called as the first witness.
However the committee is now expected to call every former minister for health and secretary general of the Department of Health, to give evidence at the hearings. This will include former Secretary general Michael Kelly, who left his post for another public sector position following the Travers report.
Minister for Enterprise Micheál Martin and the two ministers of state at the Department in December 2003, Ivor Callely and Tim O'Malley, who attended a crucial meeting at which the charges were discussed, are also expected to be called.
The committee is to meet twice a week for five weeks to accommodate the high number of witnesses it is expected to call.