The Premier League said in a statement it had decided to resist strenuously the ruling which it said would reduce the incentive for all broadcasters to invest in the acquisition of sports rights.
Ofcom said in March it would force dominant pay-TV group BSkyB to make its sports channels available to rivals at a more than 20 percent reduction to the current prices in a drive to give greater choice to consumers.
The announcement followed a three-year review and was prompted by rivals including Virgin Media and BT which complained BSkyB was anti-competitive.
The Ofcom ruling was immediately attacked by English sports bodies and BSkyB has also said it will appeal.
"By forcing Sky to sell its sports channels to its competitors at a discount, Ofcom will reduce the incentives of all broadcasters, Sky included, to invest in the acquisition of sports rights," League Chief Executive Richard Scudamore said.
"This can only have a negative impact on the ability of sport to attract a fair return on its content in an open market, which is necessary to ensure appropriate investment."
An Ofcom spokesman said it was in consumers' interests for its pay-TV decisions to come into effect as soon as possible to deliver the benefits of wider choice and innovation. "We are happy to defend our decision wherever necessary," he added.
The League has two months from the date of the decision to lodge an appeal with the Competition Appeals Tribunal.
