The Government has been threatened with a major court battle if it refuses to put a new European treaty on budget rules to the people.
Opposition parties have warned they are seeking legal advice to ensure the public gets a say on whether tough fiscal rules agreed by European leaders are imposed on Ireland.
Sinn Fein TD Mary Lou McDonald said while the issue should not end up in court, the party was determined to take all measures necessary to secure a referendum.
"We are actively receiving legal advice, that is ongoing, and we will look at any and all measures to stop the implementation of this agreement and to ensure that people have their democratic say," said Ms McDonald.
Fianna Fail leader Micheal Martin said his party was also speaking to lawyers about challenging the Government should it decide against a public vote.
Twenty-five of the 27 eurozone states agreed a new fiscal deal in Brussels on Monday night. The agreement entails stricter budgetary rules for members, including penalties for states that do not comply.
Taoiseach Enda Kenny was challenged over suggestions made by Transport Minister Leo Varadkar that Irish people would not understand the details of the treaty if a referendum were called.
Socialist Party TD Joe Higgins condemned Mr Varadkar's remarks, saying the West Dublin TD was "severely spatially challenged".
"Do you agree with your Transport Minister that Irish people are so stupid that they wouldn't be able to see what the referendum is about?" said Mr Higgins.
Mr Kenny refused to respond, saying Mr Higgins' comments were beneath him.