Fianna Fáil TD Jim O'Callaghan said the issue of Irish Water is a major issue of difference between the parties, and it should be dealt with at the outset of talks between them today.
Talks between Fine Gael and Fianna Fáil on the formation of a minority Government are reconvening today.
Deputy O'Callaghan said: "Fianna Fáil's position was clear in our manifesto (where) we said Irish Water the company should be abolished and we stated water charges should be abolished or suspended for the period of the Dáil while the (new) infrastructure is put in place.
"It's a major issue of difference between the two parties. I think it should be dealt with at the outset (of talks). The alternative is we just let that issue drift and it's dealt with on the floor of the Dáil in a month or so's time."
Meanwhile, acting Fine Gael Minister Paschal Donohoe, said the party will stand over the continued existence of Irish Water.
"We're very clear on the principle here. We want to stand over the continued existence of Irish Water (and) the continued existence of asking people to make a contribution for their water," he said.
"We will be engaging with Fianna Fáil on how that can be delivered, but we believe it must be delivered."
Today's talks come after Fianna Fáil last night admitted defeat in its own attempts to form a government led by Micheál Martin .
Fianna Fáil TDs have now agreed to re-enter talks with the party's historical rival, to "facilitate a minority government" with Enda Kenny in charge.
If this process fails, a second general election will be held.
However, significant gaps remain in policy, and Micheál Martin said he was doubtful about whether the process can be completed.
In addition, Fianna Fáil said the minority Government "must include others", suggesting the inclusion of between six and eight of the Independents and others who have been abstaining in votes.
Fianna Fáil is unlikely to sign any documents today committing to a timeframe for such a government.
The meeting of the Fiann Fáil parliamentary party last night urged negotiators not to sign anything, not to have a document committing to a timeframe or number of budgets that the government would last for, and to stick to supporting the Fine Gael-led government on a case-by-case basis.
The Independents who have abstained are adamant that they want to see a firm commitment on three budgets being delivered.