The Health Minister says he’ll do everything he can to reduce waiting lists in the next year.
Simon Harris has also admitted the situation makes him feel ashamed.
It follows an RTÉ Investigates programme that found tens of thousands of patients aren’t included on official waiting lists.
The National Treatment Purchase Fund says the figures are compiled using "international best practices".
Sinn Féin Health spokesperson Louise O’Reilly doesn’t accept that explanation.
"They’re trying to deflect and confuse the issue once again, but the simple fact is there are thousands, tens of thousands of people, waiting for vital operations who have very little confidence that they are going to get those operations or those procedures."
According to international experts, organising surgeons’ schedules could cut hospital waiting times in less than a year.
The Health Minister has asked the HSE to produce a new plan amid reports that tens of thousands of patients aren’t included on official waiting lists.
A computer system used in Macedonia reportedly saw their times improve in just eight months.
The programme uses technology that hospitals already have to centralise a diary for appointments.
Arne Björnberg, Chair of the Health Consumer Powerhouse, says it could work here, but needs to be strictly enforced.
"One example here is that one of the university hospitals was obstructing a bit, and then the Minister travelled to that hospital and told the director, in front of all his heads of clinic, that if he didn’t submit all his specialists doctors’ schedules in three days he could start looking for a new job."