James Morrissey, the spokesman for businessman Denis O'Brien, clashed with Fianna Fáil leader Micheál Martin as the row over Dail privilege continues.
Mr Martin told RTÉ's 'This Week' programme that an unprecedented situation has arisen whereby the media is precluded from reporting on Dáil business due to a court action taken by Mr O'Brien.
In turn, Mr Morrissey insisted that Mr O'Brien's sole objective is to ensure his private financial affairs are protected.
He also said that figures were being presented as fact that were "fundamentally wrong".
Cork South Central TD Mr Martin rounded on Mr Morrissey over his claims that Independent TD Catherine Murphy has been "peddling lies" and is handling "stolen information".
"Your problem, Mr Morrissey, is you're attacking people too much," said Mr Martin.
"Your attitude and your response to this is to attack the person who stands up for democracy.
"So you attack Catherine Murphy, you call her a liar, you call her a thief. And you denigrate parliament by calling it a talking shop as you did last week," Mr Martin said.
"The first thing you should do, and the public want, is for you to apologise to deputy Murphy for saying she's peddling lies, for saying she got information illegally.
"It is extraordinary charges that you are making, attempting to bully and intimidate a parliamentarian who is held in wide respect across the parliamentary divide," he added.
However, Mr Morrissey said that the Fianna Fáil leader was accepting the totality of Ms Murphy's assertions without having seen the documentation.
Mr Morrissey admitted that some of what Ms Murphy said was true, but not all of it.
He said Mr O'Brien must be treated like any citizen, who is entitled to have their financial affairs kept private.
"Micheál Martin uses the word powerful - I would have thought that all citizens rank equally, but he obviously doesn't think so," Mr Morrissey added.
He alleged that the documents had been altered before they were given to Ms Murphy.
"I think the key issue here is when information is leaked, and when it's interfered with, fundamental facts are changed.
"I don't know who changed it, but Catherine Murphy has presented as facts, figures that are not correct, and she has made statements that are fundamentally wrong.
"I don't know what documents she has. I'm telling you I am satisfied that the documents she presents as being facts contain erroneous figures and numbers," he added.
Responding to the claims, Ms Murphy said she is standing by her information."I am confident of my sources and I really am not going to comment on that.
"As far as I can be sure, I am sure. I believed what I was doing and I still believe what I am doing is in the public interest."
Ms Murphy again called for an independent inquiry into the Siteserv controversy.