The 20% of households with the lowest incomes saw the biggest impact on their earnings from rising mortgage repayments during the first half of the year, the Central Statistics Office has found.
Their debt service to income ratio rose from 32% between January and June of last year to 40.8% during the same period this year.
The CSO Household Mortgage Affordability Analysis also found that the proportion of households with tracker rates who paid 20% or more of their gross household income to service their mortgage almost doubled over the same timeframe to 13.3%.
Over the first six months of the year, the ECB increased rates six times, bringing the main deposit facility from 2% to 4%.
Tracker customers would have seen that rise passed on to them almost instantly under their bank contracts.
The experimental CSO data also shows that the median debt service to income ratio of households with tracker rate mortgages for the period 2020 to 2023 fell continuously from 10.3% in the second half of 2020 to 9.4% in the first half of 2022.
However, it then rose to a ratio of 10.6% in the second half of last year, when the ECB began the current rate increasing cycle and to 11.3% the first six months of this year.
It also found that borrowers with trackers had the lowest debt service to income ratio from 2020 to 2022 of any mortgage type.
But the first half of this year those with fixed-rate mortgages had a lower median debt service to income ratio, as tracker rates went up but fixed remained relatively static.
Because the data is based on an experimental data analysis, the CSO has cautioned that care needs to be taken when interpreting it.
"ECB rate rises have added significantly to the financial stress which so many homeowners are now under and at 4.5%, the ECB rate is at a record high," said Trevor Grant, chairperson of the Association of Irish Mortgage Advisors.
"Those struggling the most tend to be the so-called 'mortgage prisoners' - that is those whose mortgages were sold by mainstream lenders to investment funds a number of years ago and who cannot refinance as they fail affordability tests with other lenders," he stated.
"There are an estimated 70,000 of such customers - most of whom took out their mortgage before 2009," he said.
He added that a number of developments recently should make it easier to ease the pressure of higher mortgage rates on many mortgage customers, including the switching initiative agreed by mortgage lenders in September.
"Furthermore, with inflation falling, it does appear that ECB rate rises have peaked and the expectation is that the ECB will commence a round of interest rate reductions at some stage next year – possibly as early as late March or early April," he said.
"However, even if the ECB starts to reduce its rates at some point in 2024, home-loan mortgage rates are highly unlikely to fall as home loan rates have not increased at the same levels as the ECB rate has, and also, because banks are under pressure to increase returns for their savers," he added.
