Subprime lender Springboard Mortgages - which is owned by Permanent TSB - is increasing its variable rates for existing customers by a full 1%.
The hike will see Springboard's highest rate jump to almost 9.5% - the most expensive variable rate in the market.
Subprime lenders sprung up during the economic boom offering mortgage credit to borrowers who were refused by mainstream lenders
The new rates will come into effect on April 1.