The three TDs, along with Senators Katherine Zappone and Jillian van Turnhout, will become the founding members of a new political force in Ireland.
Mr. Donnelly has confirmed that discussions surrounding the creation of the new pary have already begun.
It is understood that the new centre-left party is will be unveiled towards the end of this month, and its policies are likely to focus on centre-left economic policy, social justice campaigning and political reform.
More candidates will likely come onboard once the party is fully established.