US media giant Comcast has unveiled a £22 billion rival bid for Sky in a move that threatens Rupert Murdoch's deal to take full control of the pay-TV group.
Comcast said its cash offer is worth £12.50 a share - a 16% hike on the £10.75 a share offered by 21st Century Fox under its £11.7 billion deal to buy the remaining 61% of Sky is does not already own.
The group added that it plans to agree a raft of legally-binding commitments over Sky and its investment in the UK, in particular for Sky News, while it also said it would commit to keeping the group's Osterley headquarters for at least five years.
The bid is yet to be given the backing of the Sky board, but Comcast said it was in talks with the Sky Independent Committee "with a view to obtaining a future recommendation of the acquisition".
Brian Roberts, chairman and chief executive of Comcast, said: "With its 23 million retail customers, leading positions in the UK, Italy, and Germany, and its history of strong financial performance, we see significant opportunities for growth by combining our businesses."
He added: "We also understand the role that Sky plays in UK society and in its customers' lives and we are determined to be responsible and trusted owners of Sky."