The Central Bank has imposed a fine of €4.5m on Springboard Mortgages, a former subsidiary of Permanent TSB Bank, as a penalty for overcharging 222 tracker mortgage customers over a seven-year period from 2008 to 2015.

The issue first emerged in the summer of 2015 as part of a wider inquiry by the Central Bank into the treatment of tracker mortgage customers by PTSB generally and which has led to a subsequent redress scheme at that and other banks for thousands of former tracker holders 

The average overcharge levied by Springboard amounted to nearly €19,500.

Close to €6m has been paid in redress and compensation payments as a result of its actions to date 

PTSB Bank sold Springboard to a US firm, Mars Capital, in 2014, but under that deal it must pay the Central Bank fine.

The bank has since said 1,372 of its customers across its operation and Springboard are involved in the Central Bank's probe.

Its core business is expected to receive another fine as the Central Bank's investigation continues.

This is part of an industry-wide review of up to 10,000 cases across Ireland's banking sector when customers were moved off of tracker rates during Ireland's recession.

Tracker mortgages are set at a fixed percentage or 'margin' above the ECB rate. As its rates plummeted during the financial crisis Irish customers' rates should have dropped to close to 1%.

Affected customers are expected to get compensation of close to 15% of the savings that they missed out on by being denied these rates.