Sinn Féin says it will petition the President not to sign the Water Services Bill into law, if it passes tomorrow's vote in the Senate.
The party can force President Higgins to refer the bill to the Council of State if it gets the support of a third of the Dáil and a majority of senators.
Where there are legal concerns about new legislation, the council advises the President on whether a Bill should be referred to the Supreme Court.
Sinn Féin says the bill should contain provision for a referendum to ensure Irish Water remains in public ownership.
Sinn Féin Senator David Cullinane, says there's still a possibility that the bill won't pass in the Seanad tomorrow:
