The Right2Water campaign has announced a national demonstration on Saturday March 21.
The campaign, which said it "detects no softening in public opposition to water charges", is asking marchers to assemble at Merrion Square, Connolly Station and Heuston Station at 1pm.
Mandate General Secretary, John Douglas, said: "People are not fooled by concessions or by spin from Government about the revised water charges regime."
He called the charges "inherently unfair" and claimed they "disproportionately target the poorest in our society".
He said: "We also have no doubt that once this introductory offer expires in 2018, the costs for access to water will spiral out of control and families simply won’t be able to afford them.
"All across Europe – including Italy, France and Eastern Europe – and in the United States, tens of thousands of families are having their human right to water switched off because of unaffordable water bills."
Unite official and Right2Water coordinator Brendan Ogle said: "Contrary to what Government spokespersons and sections of the media would have us believe, the Right2Water campaign has detected no softening in public opposition to the charges, and we are anticipating a significant turnout on March 21st, with buses already being organised from around the country.
"This campaign will continue until the Government abolishes domestic water charges, takes steps to permanently enshrine public ownership of our water, and returns to the drawing board to design a fit-for-purpose water policy."