Newspapers in the Independent Group were accused of bias in favour of Fianna Fáil and the Progressive Democrats by the Labour spokesman on enterprise, trade and employment, Mr Pat Rabbitte.
He said that going back to the origins of the State, there was a newspaper that was self-avowedly the voice of one political party and everybody knew where it stood.
"It developed a vigorous independence as time went on and some of the more remarkable political writers wrote for that newspaper, irrespective of what the editorial line was.
"I fear that will not continue to be the case in some of the newspapers in the Independent's stable. Many journalists will continue to be objective reporters of what they see in the political arena, but there is a manifest editorial bias and it is not necessary to be partisan, as I avowedly am, to acknowledge that."
Mr Rabbitte said most objective observers would say that Independent News and Media was gearing up to support the two parties it supported at the last election.
He saw no reason why the Oireachtas should not legislate to the effect that a concentration of media ownership, beyond fixed limits, was wrong in principle and prohibited, regardless as to whether there was proof of a lessening of competition in the market place.
Mr Rabbitte was speaking during the debate on the Competition Bill, reforming and modernising legislation relating to competition and mergers.
Introducing the Bill, the Tánaiste and Minister for Enterprise, Trade and Employment, Ms Harney, said it provided for a more focused approach to penalising anti-competitive activities, more sensible arrangements on how to handle mergers and acquisitions, and a strengthened Competition Authority, capable of making a real impact in its task of enforcing competition law.
She said media mergers which did not raise public interest concerns would, in practice, be controlled by the Competition Authority acting on the basis of the competition criterion and subject to normal right of appeal to the court.
The Fine Gael spokesman on enterprise, trade and employment, Mr Charles Flanagan, said he was a little surprised, having regard to the public interest involved, that the Valentia Eircom acquisition was not referred to the Competition Authority.