The Irish Mortgage Holders Association says the tracker scandal is the single biggest consumer rip off in the history of the state.
Some of those defrauded by Irish banks have told an Oireachtas committee of the devastating medical and financial effects on their families.
So far 20,000 cases have been uncovered, but it's estimated that could reach 30,000. People have killed themselves after banks denied them their entitlement to a low-cost tracker mortgage, victims of the scandal have claimed.
It is estimated that at least 30,000 borrowers and their families have been affected by the multimillion euro overcharging as 15 banks refused to fulfil obligations to give customers the lowest interest rate in the market.
Four borrowers have told their story to politicians in the Oireachtas Finance Committee, including Thomas Ryan, who along with his wife Claire, finally and successfully faced down their bank in the courts.
"It is absolutely appalling. They have destroyed lives all over this country," he said.
"There are people no longer with us over this. They have committed suicide. And they don't particularly give a damn.
"I have heard some of the submissions here in the last few weeks from some of the banks - it is an absolute disgrace, the generic, legalistic garbage they are churning out.
"It is appalling and an absolute disgrace. There's no other words for it."
Mr Ryan, aged in his late 40s and from Wexford, was a Permanent TSB customer who challenged its refusal to give him the tracker rate. He said the banks should be forced into making amends.
He suffered a stroke in 2013 and his wife Claire had a nervous breakdown in 2015 and lost the power of speech under the pressure of their fight to be restored to a tracker mortgage rate.
"As her husband I find it pitiful and so unjust to see my wife's previous confident and bubbly nature stripped away from her," he said.
In an emotional address to the committee, Mr Ryan explained the impact on his three children of the financial pressure and long-running battle with the bank.
"The extreme stress effects on the mental wellbeing of our teenage children is absolutely heartbreaking," he said.
"It can be so upsetting for us that I cannot begin to convey in words."
Scores of people and families were put out of their homes over the last eight years after being refused their entitlement to a tracker. The Central Bank previously put the number of directly related repossessions at 100.
It also previously estimated that up to 15,000 borrowers were affected by the issue across 15 lenders and is due to update the committee next week.
Last week Ulster Bank said it will have to pay more than 100,000 euro to some of its 3,500 customers caught up in the industry-wide overcharging scandal.Previously it was revealed that 2,100 Bank of Ireland mortgages were restored to tracker rates when the issue was identified in that bank in 2010 and 2011.
There were also about 1,400 cases of customers being denied tracker rates involving Springboard Mortgages, which was a subsidiary of Permanent TSB.
The Central Bank cannot force banks to compensate home owners for tracker issues prior to 2013.
The refusal of banks to allow customers to move on to trackers first emerged as far back as 2010 - the year taxpayers were lumbered with a multibillion-euro bailout of Ireland's banks.
Padraic Kissane, the financial advisor who has been leading the charge to get customers restored to the correct rates, said customers had been treated with arrogance by the banks, a condescending attitude and a lack of empathy and understanding.
"What moral compass do they possess," he said.
"It is financial abuse on a grand scale, contrived to deceive customers of their contractual rights."
Mr Kissane also warned he has a host of cases of bank staff and people working for legal teams and auditors associated with the banks who want to challenge the rates they have been put on but are worried about the consequences for their careers.
He told the committee there was a cartel in operation in Ireland's mortgage market. He compared one of the best rates on offer at the minute - a 10 year fixed mortgage from KBC at 2.95% compared to a 10 year fixed rate in Germany of 1.15%.
He said he would shut the banks down if he was able to open a new mortgage offering European Central Bank tracker interest rates and long-term fixed rates.
"That's what needs to happen," he said.
"I guarantee you a tracker product would be back within a month."
Mr Kissane added that the low German rates are not in Ireland and said: "The cartel wouldn't allow it."
He added: "Their figures show it. They come and they - I would describe it as boast - about their profit levels and not realise the carnage."