BT claims Sky is "afraid" after BT Sport advertising is blocked by the satellite TV giant.
Sky has been described by BT as a "Rottweiler" running from a "newborn puppy" after the satellite TV giant refused to broadcast BT Sport advertising.
BT has complained about Sky's actions to Ofcom, the UK's communications regulator, in a move that will serve to escalate the "bitter rivalry" between the two companies, reports The Guardian.
Last year, BT spent over £700million on the live broadcast rights for 38 Premier League football matches.
BT Sport coverage will start in August with the launch of two new channels, but now Sky has said it will not allow advertising for BT Sport on its own Sky Sports channels.
John Petter, managing director of BT's consumer division told The Guardian: "We're happy to take Sky's advertising, but they seem afraid of taking ours. It's like a Rottweiler running away from a newborn puppy."
BT complained to Ofcom on the grounds that Sky is showing "undue discrimination" by refusing to show adverts for BT Sport. The regulator will now investigate and intervene if necessary.
A spokesperson for Sky said: "It's entirely reasonable for us to choose not to carry advertising for a directly competing service. There are many other avenues for BT to advertise its sport channels without seeking to take advantage of the investments we've made to build Sky Sports."
They said BT would be able to run the adverts on any of Sky's non-sport channels.