The Taoiseach says he does not support the idea of absorbing water funding into the tax system
Enda Kenny has accused Fianna Fáil of a "reversal to old populism" over its stance on water charges.
Micheál Martin and his party support the complete abolition of charges.
Charges are currently suspended for a period of nine months, following the agreement reached between Fianna Fáil and Fine Gael ahead of the formation of the minority Government.
The suspension is in place while an expert commission examines the future of public water services.
Earlier this week, Fianna Fáil said it would not support a Sinn Féin motion in the Dáil next week to scrap water charges - despite it being party policy - suggesting that only a Government money bill can completely abolish charges.
In its election manifesto, Fianna Fáil pledged to abolish Irish Water and end water charges, and has said water services should be paid for through general taxation.
However, the agreement between the party and Fine Gael states that "Irish Water will be retained as a single national utility".
Speaking to reporters at Government Buildings this morning, the Taoiseach says he does not support the idea of absorbing water charges into the tax system.
Enda Kenny says a key purpose of water charges was to cut down on waste - which would not happen otherwise.
He accused Fianna Fáil of going back to old habits, suggesting they have not been able to explain "the funding that would be levied on the taxpayer".