Britain's takeover regulator ruled on Thursday that Walt Disney must make an offer for the whole of European pay-TV company Sky if it succeeds in buying Twenty-First Century Fox assets, including its 39 percent stake in Sky.

The Takeover Panel also said Disney must match Fox's 10.75 pounds-a-share offer for the shares in Sky it does not already own.

Rupert Murdoch's Fox agreed an offer to buy all of Sky 17 months ago, but is still waiting approval. In the meantime, Disney agreed to buy Fox assets, including its stake in Sky, in a separate deal, which is subject to regulatory clearance.