A new opinion poll indicates that support for the EU Fiscal Treaty remains solid, with just under half of voters in favour, while one third are opposed.
Although a date hasn't been set, the referendum is expected towards the end of May.
Just over 1,000 voters around the country were questioned for the Sunday Business Post poll between Monday and Wednesday.
These show that 49% say they will vote yes, up five points since the last poll three weeks ago. 33% say they will vote no - an increase of four points - while 18% remain undecided.
When they are excluded, the yes side leads by 60% to 40% - the same as three weeks ago.
Elsewhere, the poll shows an increase in support for Fine Gael by four points up to 34%. Labour at 15% is down one, as is Fianna Fáil at 16%. Sinn Féin are unchanged at 18% and retain their place as the second-largest party in the country currently. Independents and others have dropped two points to 17%.