Carlos Slim, the Mexican telecoms billionaire and world’s second-richest man, has waded into the battle for control of The Independent by taking a stake in the newspaper’s parent company.

His arrival on the shareholder register adds spice to a bad-tempered tussle between warring Irish businessmen Sir Anthony O’Reilly and Denis O’Brien over the parent group, Independent News & Media (INM).

O’Reilly’s family controls 28% of INM. As well as The Independent, INM owns the Belfast Telegraph and newspapers in Ireland, Australia and South Africa.

But the family faces a challenge from O’Brien, who has been needling O’Reilly for more than two years as he has amassed a stake of 21%. The company is dual-listed in Dublin and London and has a market value of £1.2 billion.

Slim’s appearance on the register adds a further twist. He has so far built a 1% stake, but this is likely to increase.

He can easily afford it. In the latest Forbes magazine ranking, Slim was valued at $60 billion, behind Warren Buffett’s $62 billion but ahead of Microsoft chairman Bill Gates on $58 billion.

He gained his fortune through ownership of Mexico’s main telecoms operator, Telmex. He also owns America Movil, Latin America’s dominant mobile player, which has more than 100m subscribers.

Analysts say that Slim could be building a stake as part of a bigger game.

O’Brien is in competition with Slim in the Caribbean mobile-phone market through his group Digicel. America Movil has been mooted as a potential buyer for Digicel, although O’Brien has stressed it is not for sale. Slim’s investment in INM could now be used as a bargaining chip to push for a deal in the Caribbean.

In a recent interview, O’Brien played down the competition from Slim in the region. “I’ve competed with companies which have been hundreds of times bigger [than us],” he said.

Insiders at INM insist that Slim took the stake without their knowledge. O’Reilly, who ran baked beans maker Heinz and is a former rugby international, has never met the Mexican. INM used to have radio and outdoor advertising interests in Mexico.

INM referred to Slim’s Caribbean activities in the questions for O’Brien that it circulated at the company’s annual results briefing in March, in an attempt to cast doubt on O’Brien’s financial capacity to mount a bid for the media group.

O’Brien is expected to continue building his stake in INM. His investment is under water after shares in the company fell on concern for the outlook for newspapers.

Nevertheless, Slim’s appearance on the share register may frustrate any ambitions to mount an all-out bid. O’Brien and O’Reilly have been clashing since 1995, when O’Brien, then only 36, led a consortium that defeated O’Reilly to win Ireland’s second mobile-phone licence, which he later sold to BT. O’Reilly struck back in 2002 to take private Eircom, Ireland’s main fixed-line operator.

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