Fianna Fáil has said legislation is needed to force banks to lower their variable mortgage rates.
It comes as Bank of Ireland yesterday announced that it is reducing its fixed-rate mortgages by 0.3%.
It has made no announcement on its variable rate however, which stands at 4.5%.
Finance Minister Michael Noonan recently met with financial institutions to ask that they reduce variable rates in line with falling ECB rates.
Fianna Fáil Finance Spokesperson Michael McGrath said that legislation might be the only way to deal with this problem.
"I firmly believe that legislation is going to be required in the Oireachtas to give the Central Bank power to intervene where a market failure has occurred - and one has occurred in the Irish mortgage market - and to put a cap on the level of rates that the banks are charging variable rate customers," he said.
"This issue is simply not going to go away.
"The Minister met with the banks a couple of weeks ago and, judging by this reaction from Bank of Ireland, those meetings have simply failed."