Taoiseach Leo Varadkar has said that the issue of refunding domestic water charges was discussed by Cabinet.
Speaking at the launch of the latest national drug strategy, Mr Varadkar said Government must still decide if it will deduct the €100 conservation grant from water charge refunds, but said it would be "logistically and legally very difficult".
Refunds will begin in the autumn and will be completed before the end of the year, according to the Taoiseach.
He said the money to repay the charges would come from taxation and Government under-spend.
Earlier the Minister for Employment and Social Protection said the issue of the refund had not been discussed in detail by Cabinet.
Speaking on RTÉ's Today with Sean O'Rouke, Regina Doherty said she has not been fully briefed on the matter.
Despite this, Ms Doherty said people can look forward to refunds from September onwards.
Asked when the Cabinet discussed the refunding of water charges, the Taoiseach said: "The Government considered the Oireachtas Committee report a number of months ago and that had provided for a refund of water charges so a decision has been made to refund the water charges.
"What we've been working out between Minister [for Housing, Planning, and Local Government Eoghan] Murphy, myself and Minister [for Finance Paschal] Donohoe in the last number of weeks is the how and when and we now believe it will be possible to do the refunds this year.
"We would anticipate that would start in the autumn and everyone would be refunded before Christmas."
Fianna Fáil finance spokesperson Michael McGrath has called for clarity on when Cabinet discussed the issue.
In a statement this afternoon, he said Mr Varadkar's comment that he had mentioned the issue of refunds at a previous Cabinet meeting "is very different to what Minister Doherty said this morning on a radio show when she stated 'I haven't been fully briefed on it, and we haven't had a Cabinet meeting to discuss it'."
Mr McGrath added: "The Taoiseach must outline at which Cabinet meeting was the issue of refunds discussed, and why wasn't Minister Doherty aware of this discussion?
"Secondly, we have heard vague references to how this €170 million refund will be funded. The Taoiseach needs to reassure the public that there are no plans to impose cuts to vital public services."
Money to come from existing resources
Speaking on RTÉ's Morning Ireland, Minister for Education Richard Bruton said the money for the refund will come from within existing resources.
The Minister for Education said the Government had some "wriggle room" within the Estimates and the money would be found within that.
The sum involved is around €170m and consists of water charges paid by householders before the charges were abandoned.
Close to one million customers of Irish Water paid, or partially paid, water charges before they were ended officially earlier this year.
Fianna Fáil's environment spokesperson welcomed the commitment to refund all domestic water charges, but said he would like some clarity on where the money will come from.
He said he would be happy to meet Minister for Housing Eoghan Murphy to discuss it further.
Green Party leader Eamon Ryan described the Government's announcement as a public relations kind of approach but said there is no legislation to treat water quality seriously.
Mr Ryan said he has called on Government to look at introducing legislation for charging for excess use and other issues, which he says were agreed by the Committee on the Future Funding of Domestic Water Services.