The tracker mortgage scandal will cost the banks around €1bn, the Central Bank has said.
Some €316m has been paid out to borrowers who were wronged by banks which denied them access to low interest rate tracker mortgages.
And with about €900m - €600 euro for compensation and redress and €300m for costs - already set aside to cover the rogue lending, the Central Bank warned the bill will escalate when fines and regulatory bills are added.
Central Bank governor Philip Lane told the Oireachtas Finance Committee that the controversy was unprecedented after 33,700 borrowers were denied the right to go back on to a tracker rate and others were denied access to the correct rate on a tracker.
The total number of borrowers affected is expected to run to another several thousand.
"Lenders are counting the cost of this scandal," Mr Lane said.
Central Bank chiefs told the committee that it is running four enforcement cases over the tracker affair.
Derville Rowland, Central Bank director general, said they do not believe in "going after juniors" for regulatory breaches.
"It's often easy to find evidence against the fella who is proximate to the issue but that does not get you to the directing mind and it does not get to the actual senior responsible culpable people," she told the committee.
"We are firmly committed to the ideology that it's right to hold individuals to account."
The Central Bank said it had received 50 protected disclosures from whistle-blowers in 2016 and 93 in 2017. It took in 28 protected disclosures from whistle-blowers related to banks across a range of issues.
In a run-down of the scale of the tracker mortgage scandal, the regulator said three quarters of the 13,000 customers first identified have been compensated. Most of the rest will get their money by the end of March.
The 13,600 customers accepted since last October as being wronged can expect to get their money by the end of June.
Another 7,100 borrowers had been discovered in a previous trawl.
The committee previously heard about the human cost of the scandal including suicide and long-term health problems.
Mr Lane said: "I acknowledge that this work has taken time to complete and I am conscious of the devastating impact that lenders' failures have had on customers, up to and including the loss of their homes and investment properties.
"I acknowledge also that no amount of money will ever fully compensate a person or family for the trauma involved in losing their home."
Mr Lane also warned that board members and senior personnel have significant legal obligations to report possible breaches of regulations to the Central Bank and suspected criminality to gardai.
Top bankers are now being asked to sign and confirm they know their obligations, Mr Lane said.
"The culture of a firm is the responsibility of that firm," he told the committee.
"In particular, the members of its board should constantly be asking questions of themselves and their firm."