Richard Boyd Barrett has said Labour is ignoring "overwhelming demand for radical change" by ruling out going into government.
The Solidarity-People Before Profit TD says talks with Sinn Féin have been "very positive".
His group will be meeting with the Green Party in the days ahead and has been reaching out to left-leaning independents.
Deputy Boyd Barrett said people want action, and he wants unity on the left.
He said: "We had a very positive meeting with Sinn Féin, we're hoping to meet the Greens in the next couple of days, we've had communications with them.
"We are keen to talk to others on the left and independent left TDs who have been elected about a possibility of bringing about a government that's going to bring about a radical transformation for a more equal and better country."
