Labour leadership candidate Alex White says the addition of two Government Senators to the Banking Inquiry "gives politics a bad name".
The Junior Health Minister's comments come after it was revealed that Fine Gael's Michael D'arcy and Labour's Susan O'Keefe will be added to give the coalition a majority on the inquiry.
Alex White says he doesn't believe a Government majority is "critical" to the inquiry's success, and disagrees with the later additions to its membership.
"This, frankly, is the kind of behaviour that gives politics a bad name," he said.
"I think the critical thing about a banking enquiry is that it gets underway. I don't think it's critical that there's a Government majority on the banking inquiry.
"What's most important is that it gets up and running, that we get answers - and the public gets answers - to questions that have been around now for quite a few years."
Fianna Fáil's Ned O'Sullivan even compared the Taoiseach to Adolf Hitler.
"The Taoiseach has now become a bit of a danger himself - now he's coming in … asking us to do something that Hitler himself with the enabling act would have been ashamed of. Ashamed of!" he said.
And the party's senator Paschal Mooney said the Government was making a mockery of Irish politics.
"When this Government came to power, it initially said that it was going to be ushering in a new era of transparency," he said.
"But the events of the last week have shown that this has been a hollow truth - and in fact what we are now witnessing is political skulduggery at the very highest level."