According to a report in the Daily Telegraph, Sky wants its bitter rival to withdraw the campaign, which calls for UK ISP’s to be honest about the broadband speeds they deliver.

Sky’s lawyers issued an ultimatum to Virgin Media on Monday, giving the company eight hours to stop the campaign on pain of a complaint being made to the Advertising Standards Authority (ASA).

In a legal letter seen by the Telegraph, Sky accused Virgin’s campaign of being “grossly misleading” and complained at the implication, in an advert run over the Christmas period, that Sky’s broadband was “stuck in the slow lane.”

Sky’s lawyers, Osborne Clarke, said the adverts: “clearly go beyond the scope of robust and objective comparison and amount to an unjustified denigratory attack on Sky and its business practices.”