DENIS O’BRIEN has spent about €19.4 million to increase his shareholding in Independent News Media to 18.7 per cent.

This takes his stake ahead of the holding of Sir Anthony O’Reilly and his family, who own 14.65 per cent, and makes him the group’s biggest single shareholder.

INM’s share price rose by 5.2 per cent yesterday following the announcement to 14.1 cent. It is understood Mr O’Brien acquired the shares at 11.5 cent each.

Market sources said the stock was bought from Bank of Ireland, which up to that point held a 4.7 per cent stake in the business.

Bank of Ireland was one of the bondholders that participated in the debt for equity swap last year as part of a major financial restructuring by INM, aimed at reducing its debts. The bank never intended to be a long-term holder of the stock and placed it on the market in recent days.

Mr O’Brien’s latest stakebuilding surprised market watchers but is seen as highly significant, although he is not expected to buy more shares in the short term.

A spokesman for Mr O’Brien declined to comment on his latest purchase of shares. It is not clear if Mr O’Brien will seek to increase his influence at INM. He has three representatives on the 11-person board – Leslie Buckley, Lucy Gaffney and Paul Connolly.

Mr O’Brien held 26 per cent of INM before a major financial restructuring last year, which diluted existing shareholders.

Mr O’Brien opposed the restructuring, which also involved the sale of certain assets. These included INM Outdoor in South Africa, which was sold for a net €95 million to Helios Investment Partners.

Alternative proposals put forward by Mr O’Brien at the time of the restructuring were rejected by bondholders. Mr O’Brien has had an on-off battle with the O’Reilly family and the board of INM about the way the company has been run and he has been described as a “rebel” investor.

Separately, INM non-executive director Bengt Braun, who joined the board in March, announced yesterday that he has acquired 450,000 shares in the company at a cost of €52,605.

This prices the shares at 11.69 cent each, marginally higher than the price paid by Mr O’Brien. Mr Braun is vice-chairman of the Bonnier Group, one of Scandinavia’s largest media companies.