While Sky is obliged by law to carry any broadcaster's channels, should it agree fair terms, Virgin Media faces no such obligation.
In a letter to Ofcom, Canis Media - which effectively acts as a broker for third-party channels - has insisted the Virgin platform should be opened up to channels in a similar way to Sky's regulated platform. Canis Media chief executive Ed Hall urged Ofcom to engage in an industry-wide consultation.
A Sky spokeman said: "While satellite has been an open platform for years, we're very aware of the problems caused by Virgin Media's closed network. After talks about a wholesale deal broke down last year, customers were denied access to Sky's basic channels because Virgin refused to allow us to retail directly to consumers on its platform."
Virgin Media declined to comment, but Ofcom said it is not actively looking into the issue as part of its pay-TV market investigation.