The European Central Bank has cut its key interest rate by half a percentage point to a record low of 1.5%.
Rates have now fallen by 2.75% since October.
Read about how the rate cut will impact your mortgage here
The ECB has signalled that further reductions in interest rates are possible, as its experts forecast that the euro zone economy could shrink by more than 3% this year.
President Jean-Claude Trichet stressed that he could not rule out further moves.
He also said the ECB's governing council was studying other possible measures, known by economists as quantitative easing.
Permanent TSB, KBC Homeloans, EBS, Irish Nationwide and Halifax and Bank of Scotland (Ireland) said the full half a percentage rate reduction would be passed on to customers with variable and tracker rate mortgages.
Bank of Ireland and ICS Building Society also confirmed this afternoon that they will pass on the full ECB rate decrease across their tracker and standard variable rate mortgage products, for new and existing owner-occupier customers.
But National Irish Bank has said that it will not be passing on the ECB rate cut to standard variable mortgage rate holders, though tracker rates will fall by 0.5 points.
NIB said it had signalled in January that it saw little scope to pass on future rate cuts. It added that a range of deposit rates for savers would also not be reduced.
Ulster Bank and First Active will pass on the cut to tracker mortgage holders, but Ulster Bank said the variable rate was 'under review'.
The Fed and Bank of England have already begun to buy commercial paper directly from businesses in one form of what is called quantitative easing, basically running money-printing presses overtime, to underpin activity.
The Bank of England earlier announced its move, saying it would buy assets worth a total of £75 billion sterling in a drive to help the British economy by expanding the money supply.
It also cut its interest rate from 1% to 0.5%, a record low for the 315-year-old bank.
The US Federal Reserve and Bank of Japan's main rates are essentially zero.
Eurozone GDP shrank 1.5% in the last quarter of 2008 and it will slump further early this year, while inflation remains tame at 1.2%, well below the ECB's target of just under 2%.
