Unite is calling for a public boycott of the property tax which it says can cause huge distress and despair among society.
The trade union is one of the largest in the country. It is urging the public to hold firm and start by not engaging with Revenue.
Unite has joined forces with the Campaign against Household and Water Taxes and will be joining a day of protest on April 13th.
This is to coincide with a meeting of European Union Finance Ministers at Dublin Castle.
'Fight can still be won'
But the Revenue Commissioners have threatened to deduct the tax at source from pay packets and even social welfare if they do not pay. The Commissioners say they have sent more than 1 million letters to homeowners in recent weeks.
Some €1.3 million has already been collected. That is according to figures from the Department of Finance published on Wednesday.
Regional Secretary of Unite is Jimmy Kelly. He maintains that they can still win the fight against the tax.