Poor 'hardest hit by crash'
The poorest 10% of people in Ireland have lost almost a fifth of their disposal income since the crash, it was claimed.
Social Justice Ireland said the gap between the rich and poor has widened as those with most money only lost 11.4% of their spare cash.
Dr Sean Healy, director, said low and middle-income Ireland have borne the major brunt of adjustments over the past five years.
"The situation would be even worse if cuts in services and increased charges were included in calculations," he warned.
The think-tank's study claimed budgets introduced under the Troika programme were regressive, taking more as a percentage of income from those who have least.
It also stated the real impact was even more regressive because its calculations do not include the impacts of reductions in services and increased charges introduced in these years, which impact disproportionately on the most vulnerable.
"Ireland's poorest 10% lost 18.4% of their real disposable income since the start of the crash in 2008," said Dr Healy.
"By contrast the richest 10% lost 11.4%.
"The richest 20% of the population were the only ones whose share of the total disposable income grew significantly in this period.
"This confirms the widening gap between low and middle-income Ireland on the one hand and the richest 20% on the other."
Michelle Murphy, research and policy analyst with Social Justice Ireland, said Government did have choices and could have introduced fairer budgets. Instead the choices they did make increased inequality in Ireland.
"Ireland had to reduce its budget deficit in recent years but research produced by the IMF shows that how Ireland's Government chose to do this was always likely to produce greater inequality and higher levels of unemployment," she added.
"Other options were available to Government but they chose to protect the rich at the expense of the rest of us."