Virgin Media is reportedly angry about BT's decision to allow BT Sport channels to be offered to EE mobile subscribers free of charge.
According to a source quoted by the Telegraph, Virgin Media is "absolutely furious" that EE's monthly subscribers now have six months of free access to BT Sport via a mobile app.
The promotion is part of an effort to bolster links between BT and EE following the former's takeover of the mobile operator.
However, Virgin Media is a direct competitor of EE thanks to its Virgin Mobile service and rents capacity from the company.
Virgin Media also pays more than £120 million a year to BT in order to give its subscribers access to BT Sport channels.
The company is now understood to be alleging that BT's promotion with EE breaches the contract it has in place, which states that wholesale access to BT Sport cannot be offered at a lower price than it is paying.
Virgin Media is therefore calling on BT and EE to suspend the promotion, on the grounds that it is effectively a wholesale deal at zero cost.
EE is promoting the deal with a TV advertisement fronted by Kevin Bacon, who announces it in the persona of a presenter covering a breaking story on a rolling sports news channel.
Ex-Manchester United star Rio Ferdinand, Harry Redknapp and Jose Mourinho also feature in the commercial.