Sky is likely to be accused of abusing its dominance in the market by overcharging its rivals for access to its premium channels.
This is a complaint that has been levelled at Sky by a number of its competitors, including ITV Digital. ITV Digital says it is paying over the odds for carrying Sky's premium sport and movie channels.
The investigation is the first to be launched by John Vickers, the regulator's new director general.
The Rupert Murdoch-controlled satellite broadcaster could ultimately be forced to cut its prices -- a move which has been anticipated by City analysts.
The investigation was originally due to have delivered its findings in June, but was delayed because of the general election. However, once its findings have been released there is likely to be a long process of negotiation.
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