Micheál Martin has lashed out at Fine Gael's John Paul Phelan for interfering with the electoral process over the two 'cold storage' EU seats.
The Fianna Fáil leader said there is still "ambiguity" around the law which was brought in to allow for the two extra MEPs who will not be able to take up their seats until Britain leaves the EU.
It follows considerable controversy over transfer votes for the two final seats in Dublin which brought a halt to counting in the European elections overnight.
However, before the accounting officer had returned with his decision on the matter, Minister of State Mr Phelan went on morning radio to give his view on the matter.
Arriving at the Ireland South count centre in Cork, Mr Martin said he found Mr Phelan's intervention "incredible".
"I think it was inappropriate for him in the first instance to make the comments he made on Morning Ireland because the returning officer was in the process of making a decision.
"Ministers should not interfere in the electoral process when it's in play and when there are appointed authorised officers under the law who are there to do that."
Mr Martin added that the Minister of State showed that he was "out of his depth" when he had to go back on air to correct his Morning Ireland interview just a few hours later
"If the Minister is not in command of his own legislation, I think it's lamentable indeed.
"It has been a shambles and I think everything that Minister turns his hand on ends up in some bit of a mess.
He added: "I think it's clear there is ambiguity there in terms of the Act, clearly it's a matter for returning officers in accordance with the law."