Peadar Tóibín has claimed Sinn Féin TDs have 'zero influence' over policy decisions.
The Aontú leader, a former member of the party, has said paid organisers have too much power over the organisation.
He resigned from Sinn Féin in 2018 after he was suspended from the party for six months, for voting against abortion legislation.
On Tuesday, he said: "I felt when I was in Sinn Féin I didn't have influence as a TD.
"I've always been of the instinct that a TD's first responsibility should be with the constituents - the people who vote them in.
"When the party gets in-between the TD and the citizens, that creates a difficulty - both democratically and also with regards to the needs and the interest of the electorate.
"I don't think Sinn Féin is unique in this regard - I think often times political parties put themselves first, rather than the needs of the constituents."
He continued: "The difficult that arose for me - I remember on one particular occasion People Before Profit were pushing a bill in the Dáil, and that bill was to delete parental choices when it comes to the ethos of schools.
"I had checked the Sinn Féin Ard Fheis motions and I found that they were actually very contradictory - some motions said that there should be parental choice when it comes to ethos, others said there shouldn't be parental choice when it came ethos."
He said following a party debate, "staffers turned around and read out the decision of that meeting and I tackled him on it.
"I said 'we were told to have a debate and make a decision, but you've read out a pre-written script of what the decision is'.
"I was met with a shrug."
"It became very clear on that occasion... that here we were as TDs, elected by the people with 10,000 votes, and unelected staff were dictating to me which way we should vote".
"One of my gripes with the party before I left was that there was a democratic centralism within that party".
He said that the party had to pledge that they would be led by the Ard Chomhairle.
"Every time anybody stands for election, at any level, they sign a pledge to state that they must follow the direction of the Ard Chomhairle".
But Deputy Tóibín says this is the same as other parties "to a certain extent".
"In my experience, if the Ard Fheis makes a particular decision and creates a particular policy and then a party is in government and a crisis arises - and information arises that wasn't available to the Ard Fheis when it made its decision, you could have that party... tied to a policy that was no longer relevant".
In a response, Sinn Féin said in a statement: "The story is utter nonsense and it is clear that Peadar is desperately seeking to make himself relevant and grab some valuable airtime in the penultimate week of an election campaign".