The Head of the Workplace Relations Commission (WRC) says he has no intention of standing down, despite calls from SIPTU's President for him to resign.
A war of words has broken out between the WRC's Kieran Mulvey and SIPTU's Jack O'Connor over the Luas dispute.
The Luas dispute is ongoing with two more strike days this weekend, after drivers overwhelmingly rejected a proposed deal last week.
Mr Mulvey used an interview this morning to suggest SIPTU dropped out of contact after drivers turned down the deal.
Jack O'Connor denied the accusation and called for Mr Mulvey to resign.
Mr Mulvey later said he thought the offer was the best that could be achieved, and said he disagreed with the SIPTU chief that expressing this view undermined his position.
Speaking to Newstalk Breakfast, Jack O'Connor said he was "astonished" by Mr Mulvey's comments on RTE's Morning Ireland programme.
"At first I thought it was an April Fools' joke or something, but then I realised it was all serious," he said.
"Once you come out on the public airwaves, on prime time radio, and attack one party to the dispute - in this case the Luas workers - then you are no longer credible as a mediator," he added.
Meanwhile, the Transport Minister has rejected calls to step in to stop this weekend's strike.
Paschal Donohoe said he if he interferes in the talks directly he would undermine the work of the WRC.
He told Breakfast that the WRC is "the only forum in the country in which a matter like this can be resolved":
In the latest stoppage by drivers - in a row over pay - trams will not run on Saturday or Sunday.
It follows the strikes held on Easter Sunday and Monday.
In a statement yesterday, the CEO of Transdev UK and Ireland, Nigel Stevens, said current demands are 'totally unaffordable and will not be countenanced'.
Speaking to Pat Kenny today, Transdev Ireland's managing director Gerry Madden said he does not think that Kieran Mulvey needs to step down from his role at the WRC.
"I can say from personal experience, having spent 27 hours in there, I didn't get any sense that he has any bias one way or the other," he said.
He added that "anybody who tries to come in and find a way to bring sides together to resolve a dispute... they're welcome as far as I'm concerned":
Drivers had been looking for a pay-rise of up to 53%, and last week rejected a pay offer of between 8% and 18% over 33 months.
They cited the reduction of entrants' pay levels, increased productivity demands and a lack of trust as reasons behind declining the deal.
There are two additional strikes days planned for the end of the month - on April 23rd and 24th.
