People Before Profit's Bríd Smith is bringing a legal challenge over the block on the Climate Emergency Measures Bill.
The bill was backed by a majority of TDs after a debate -- but the Government has stopped it going to committee stage.
Dublin TD Smith says the way the Government has been blocking private members' bills is a subversion of democracy.
She believes she has a strong case to make.
"There are a number of grounds on which the blocking of this bill is immoral, inappropriate, and doesn't stand up to any kind of scrutiny," she said.
She said a coalition of campaigners will be joining her in the case.
"We'll be talking tomorrow to legal advisers and to other groups -- it won't be just me or People Before Profit -- there'll be many groups involved in this legal challenge."
