Minister for Communications Pat Rabbitte has described the resignation of Independent News & Media chief executive Gavin O’Reilly as a “thunderclap” in the media sector.

Mr O’Reilly’s decision to quit ended 39 years of direct control by his family of the country’s largest media group.

The move follows weeks of speculation that INM’s largest shareholder Denis O’Brien, who owns 22 per cent of the business, would seek to have Mr O’Reilly removed from his post at the company’s annual meeting in early June.

Mr Rabbitte said the departure of Mr O'Reilly represented “the end of an era” for the business and for the sector.

He told The Irish Times that it was not the Government’s task to become involved in boardroom conflicts.

However, the Minister said the Government was very concerned about the concentration of ownership in the sector.

On the prospect of Mr O’Brien assuming control of IN&M, Mr Rabbitte said his department would soon publish legislation covering competition and media ownership and he did not want to enter the process with any “preconceived conclusions” regarding Mr O'Brien's position.

Nevertheless, he said the Government must be enabled to respond to what he described as the “undue concentration of ownership”, especially, where there may be cross-media ownership.

“We have to be careful that capacity is there in regulatory terms to ensure that diversity of content and diversity of ownership obtains.”

Mr Rabbitte said the media had to be treated differently from other enterprises because of its importance in determining “the character of our public discourse and its influence on the quality of our democracy.”

He said it was too early to judge whether Mr O’Reilly’s decision to quit meant anything more than just a change of  chief executive.