There's a call for the next government to take in an extra €2.5bn to €3bn per year in taxation.
Social Justice Ireland is putting forward the new tax take target in its Socio-Economic Review released today.
It says Ireland's tax-take must increase gradually towards the European average to tackle issues around housing, healthcare, childcare and public transport.
The organisation's calling for a minimum effective corporation tax rate of 6% to be implemented.
It's proposing a reform of tax break, in particular those applying to high earners.
They're also suggesting that the two main income tax credits be made refundable "to help make low-paid work more rewarding".
CEO of Social Justice Ireland Dr Sean Healy said more tax is needed to provide services.
He observed: "We should be collecting enough tax that's required to achieve the kind of outcomes we're looking for in terms of the economy, services, infrastructure and so on.
"We have to do that in a fair and sustainable manner.
"It can be done, but would require a number of changes to the tax base and reform of the structure of the Irish taxation system."
Government formation
Fine Gael and the Green Party will hold exploratory talks today, as government formation efforts continue between the different parties.
Fianna Fáil is also expected to hold a policy exchange with Fine Gael in the coming days.
It comes as the Fianna Fáil leader Micheál Martin comes under increasing pressure from members of his own party to get a deal done by the end of next month.
The Greens, meanwhile, have been holding talks with a number of parties - including over seven hours of policy discussions with Sinn Féin last week.
Party leader Eamon Ryan has said there is a "willingness amongst the other leaders to engage with the Green Party and the increased mandate of the party".
An opinion poll published over the weekend suggested Sinn Féin support has surged since the election.
The survey was conducted by Behaviour & Attitudes for The Sunday Times.
It shows Mary Lou McDonald's party as 10 points higher than its general election result in the first opinion poll since last month's vote.
Fine Gael was down almost three points to 18%, Fianna Fáil was down two to 20% and the Green Party is down one to 6%.
Sinn Féin's support seems mirrored in party leader satisfaction: Mary Lou McDonald is up 13 points to 53%.
