ITV Digital's ongoing battle with Sky has led to the European Commission (EC) launching an investigation.
Officials are to look into Sky's relationship with the Discovery channel and the Disney channel following a complaint from its rival.
These agreements prevent Discovery or Disney offering their entertainment channels to ITV Digital, which is the second biggest provider of digital TV in the UK.
The new attack on Sky follows ITV Digital's launch of a rival commercial football package for pubs, which is due to go on air next month.
The Office of Fair Trading (OFT) is also carrying out a separate investigation into Sky's dominance of the pay-TV market in the UK. Sky has more than five million subscribers while ITV Digital has 1.1 million.
The OFT inquiry was launched last December after ITV Digital claimed that Sky charged unfair prices for the use of some of its TV channels, including sport.
Sky said there was no case to answer in either investigation. "Agreements with these channels have had no appreciable impact on the competitive situation," the company said in a statement.
The OFT is not expected to publish its report until September because the inquiry has been delayed for two months because of the complexity of the case.
The EC's anti-trust investigation is likely to last many months. It is based on ITV Digital's claims that Sky's agreements with Discovery and Disney unfairly prevented other operators from screening the channels' programmes. The accusations do not cover any sports broadcasts or channels in its commercial pub package.
In a statement, the EC said: "The complainant alleges that the exclusivity clauses in contracts between Sky and these channels break competition rules."
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Sky offers new deal (July 19, 2001)
ITV to launch pub sport package (May 17, 2001)