The EU-funded report identified a number of policy weaknesses which allowed billionaire businessman Denis O’Brien to have a dominant position in Irish media.

He owns 29.9% of the country’s biggest newspaper group, Independent News and Media, and is the principal shareholder in Communicorp which owns two national radio stations, Today FM and Newstalk as well as several local radio stations which account for 20% of the radio market.

The report by the European University Institute’s Centre for Media Pluralism and Media Freedom said existing levels of media concentration, particularly in print and broadcast media, already exceeded the recommended maximum 20% market share described in the 2014 Competition and Consumer Protection Act.

Only Finland, Lithuania and Luxembourg were deemed to have higher concentrations of media ownership than Ireland in a study of 19 EU member states.

The centre said that Irish politicians had been reluctant to seriously consider the issue.

“The obvious means to address this is to adjust the legislation so that it applies retrospectively,” the report concluded.

It said Irish politicians cited the strong defence of property rights which were granted protection under the Constitution as a reason for failing to act.

However, the centre said: “Given that freedom of expression is also explicitly defended in the constitution, there is clearly a case to be made for retrospection.”

When issuing new media ownership guidelines last year, then communications minister Alex White said he did not believe they could be applied retrospectively because of constitutional protections.

The report also identified a risk that some minority groups in Ireland were “manifestly under-represented” in mainstream media. It said some social and cultural groups as well as local communities had difficulties in accessing media.

RTÉ schedules rarely included any programming focusing on the interests of ethnic minorities with the exception of Irish-language speakers, the report said.

“Given the transformation of the ethnic profile of Ireland since the 1990s, the presence of the ‘new Irish’ has not been reflected among the cohort of Irish media professionals or in terms of their media representation,” the centre said.