Comcast gatecrashed Mr Murdoch's attempt to buy the 61% of Sky his company did not already own in February while the Fox deal awaited government approval.
Murdoch's Fox said the performance of Sky since December 2016, including its renewal of the right to show English Premier League matches at a lower price than expected, justified its higher offer.More news: Former Apple Employee Charged with Stealing Autonomous Vehicle Trade Secrets
Sky shares traded at £14.90 as of 9:55 am in London.
The battle for Sky intensified on Wednesday night as Comcast raised its bid for Sky, valuing the pay TV giant at £26bn.
Its bid to buy the rest of the shares has been delayed by a series of regulatory investigations, first by Ofcom, the telecoms and broadcasting regulator, and then by the Competition & Markets Authority, the UK's competition regulator. "We have long admired Sky, which we believe is an outstanding company and a great fit with Comcast. The enhanced scale and capabilities of the combination will enrich Sky's ability to continue on its mission for years to come, especially at a time of dynamic change in our industry".More news: Being dead is a ‘breach of contract,’ PayPal tells grieving husband
The skirmish for control of Sky is being fought in the shadow of an even bigger battle - a struggle for control of prized entertainment assets owned by Fox, including its stake in Sky.
Sky now operates in Britain, Ireland, Germany, Austria and Italy. If true, this would be in violation of security rules and may well block - or at the very least stall - Disney's acquisition of 20th Century Fox and its precious entertainment assets. The 39% stake in Sky now owned by Fox is part of that larger prize, and both Comcast and Disney see the pan-European pay-TV company as one of the most valuable elements of the deal.
Sky has become a pawn in a much larger struggle between Comcast and Disney (DIS), which are locked in a bidding war for most of Fox, including its existing stake in Sky.More news: Follow the World Cup semifinal between England and Croatia
In a statement Comcast, a $155 billion United States cable television giant, said that its latest offer represented a premium of approximately 5.4 per cent to the 21st Century Fox offer, "implying a value of approximately..."