US cable TV giant Comcast has made a £22.1bn bid for Sky, challenging an existing offer from 21st Century Fox.

Rupert Murdoch’s 21st Century Fox had already agreed an £18.5bn deal to buy the 61% of Sky it does not already own.

Comcast is the biggest US cable TV firm. It also owns the broadcast TV network NBC and Universal Pictures.

Comcast chief executive Brian Roberts called Sky "an outstanding company" and said he was "confident" the offer would be cleared by regulators.

Mr Roberts added that the whole of Sky will be looking to acquire over 50% of the Sky shares.

Comcast said its bid of £12.50 a share was 16% higher than the 21st Century Fox offer.

Sky's shares jumped more than 18% to above £13 in early trading on the London Stock Exchange.