US cable TV company Comcast has launched a £22.1bn takeover bid for Sky, challenging Rupert Murdoch's 21st Century Fox.
Comcast offered £12.50 for each Sky share in cash, which it said marks a premium of 16 per cent on Fox's current offer to buy the 61 per cent of Sky it does not already own.
Shares in Sky rose more than 18 per cent at the market open to 1,305.5p.
“We think Sky is an outstanding company. It has 23m customers, leading positions in the UK, Italy and Germany, and is a consistent innovator in its use of technology to deliver its customers a great experience," said Brian Roberts, chairman and chief executive of Comcast.
Roberts said Sky would be very valuable to the US group as it looks to expand internationally.
"We would like to own the whole of Sky and we will be looking to acquire over 50 per cent of the Sky shares. We are confident that we will be able to receive the necessary regulatory approvals," he added.
Fox has been forced to make a number of concessions as the Competition and Markets Authority (CMA) probes its offer to buy Sky. The CMA has said Murdoch's influence over Sky News would need to be reduced.
Roberts said the UK "is and will remain" a great place to do business, and said Sky's UK headquarters would remain at the Osterley campus in Middlesex.
Linda Sullivan, partner and head of media and digital at Cavendish Corporate Finance, said Comcast's bid illustrated the huge strategic challenges facing broadcast companies as digital and online streaming services force increased consolidation in the industry.
"The proposed £22.1bn Sky takeover would cement Comcast’s position as the most powerful cable operator in the US and would vastly expand its international reach," Sullivan said.
"Whether or not this is a strategic move designed to force Fox’s hand, the bid is sure to raise questions surrounding the plurality of the UK media and whether such a monopolised marketplace is good for consumers.”
Sky noted the announcement from Comcast and told shareholders to take no action.
"The independent directors of Sky are mindful of their fiduciary duties and their obligations under the UK Takeover Code.
"Since no firm offer has been made at this point, shareholders are advised to take no action," Sky said.