KBC Bank has tightened its rules on lending.
The bank now requires first-time buyers to have a deposit that is 20% of the value of property being purchased.
Up to now, it would provide a mortgage if buyers had a deposit that amounted to 10% of the value of the property.
The bank claimed it had changed its lending criteria because it wanted to act in a “prudent and sensible manner”.
Last week, it said that more than 15% of its Irish loan book of €16bn was in arrears of more than three months at the end of September.
Brokers said it was one of the few lenders active in the first-time buyer market.