Independent TDs Catherine Murphy, Róisín Shortall and Stephen Donnelly are to launch a new political grouping.
Last month it emerged the three were in talks about an alliance.
In a statement today, the three TDs confirmed they have been engaged in ongoing discussions for some time and have “agreed to launch an exciting new political venture”.
“We are excited to be working together to offer a new credible political choice to the Irish electorate,” they said.
A formal event to mark their launch will be made on Wednesday.
Ms Murphy is a TD for North Kildare while Mr Donnelly represents Wicklow. Ms Shortall, a TD in Dublin North West, resigned from the Labour Party in September 2012 and is a former minister of state.
All three are expected to retain their seats in the next general election.
Tilting right
While Mr Donnelly is seen as tilting towards the right in economic policy, in contrast to the left-leaning views of the other two TDs, all three would be left-of-centre on social policy.
The move follows the establishment of a new political party Renua, led by former Fine Gael minister of state Lucinda Creighton.
Meanwhile, Shane Ross and Finian McGrath are attempting to develop an alliance of Independent TDs and councillors.
The new grouping would compete with this alliance if it is formed - and to a lesser extent with Renua - for the support of voters who say they do not support any of the established parties. That cohort has consistently ranked over 20 per cent in polls over the past two years.