Irish workers are paying more tax today than they were a decade ago.
In a pre-budget submission, the Irish Tax Institute says take-home pay for a single person on €35,000 is down by nearly €1,000.
Those on €75,000 take home 5% less than they did in 2008.
Meanwhile, Social Justice Ireland says most proposals for tax cuts benefit the better off more than lower earners.
Dr Sean Healy from the organisation says only two proposals would be fair for all.
"Just two income taxation proposals currently under consideration for Budget 2019 would produce fair outcomes: an increase in the personal tax credit for everyone or a reduction in the 0.5% and 2% USC rates," he said.
"While there should be no net reduction in tax in Budget 2019, a study conducted by Social Justice Ireland, published today, shows that the impact of most income tax proposals currently being considered by government would give far greater benefit to people earning higher incomes than to lower income employees.
Read the Fairness and Changing Income Taxes: September 2018 study here: