Digicel, a mobile phone operation founded by Mr Denis O'Brien in Jamaica, has begun a legal action against British telecoms firm Cable & Wireless (C&W).
According to the Financial Times, Digicel says C&W is delaying an interconnection agreement and obstructing it from launching its operation on the Carribbean islands of St Lucia and St Vincent.
Digicel launched its mobile operation in Jamaica in 2001.
Shares in C&W slumped this week following media reports that its Caribbean operation was under growing threat from Digicel.
The publication of a confidential internal company report on Tuesday sent the firm's shares sharply lower.
The article published by the Financial Timesquoted extensively from the report, which was commissioned by Cable & Wireless to assess the threat posed by Mr O'Brien's mobile firm.
The report shows Digicel captured 65 per cent of the Jamaican market in just two years and has monthly revenues of $16.7 million.