Denis O'Brien has increased his stake in Independent News & Media (IN&M) again and now holds 19.34 per cent of the company's shares.
Sir Anthony O'Reilly and his associates are understood to hold just over 28.2 per cent.
However, both stakes will be diluted following IN&M's acquisition in January of South African advertising company Clear Channel Independent through the issue of new shares
Mr O'Brien has not made clear his plans for his IN&M stake but has been critical of the management of the group.
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At 11.45am, IN&M shares were marginally down on the Iseq, off one cent at €1.96 just above year lows. The shares are down from highs of €3.91 last summer.