Some of the world's biggest buyout firms are weighing a £10bn takeover approach to the owner of O2 after its plans to merge with rival mobile network operator Three were blocked by European regulators.
Sky News has learnt that Apax Partners, CVC Capital Partners and KKR are examining a possible offer to O2's parent, Telefonica.
Some of the potential private equity bidders have held preliminary talks with bankers about financing a deal.
City sources cautioned that there were several factors which could prevent a formal offer being made to the Spanish owner of O2, such as a bid from Liberty Global, which owns Virgin Media.
Mike Fries, Liberty Global chief executive, said this week it would be "strange" if his company did not evaluate a bid for O2.
Telefonica's hopes of combining O2 with Three to create the UK's biggest mobile phone group were dashed on Wednesday when the European Commission said the merger would damage consumers' interests.
Apax and KKR had previously worked together on a bid for EE prior to its takeover by BT Group.
Other private equity firms with significant experience of European telecoms deals are also expected to examine bids for O2 given the amount of capital available to private equity firms with large funds.
For Telefonica, a sale to Liberty or private equity groups would not involve the competition risk inherent in the Three transaction.
The collapse of the merger means that separate deal arranged by CK Hutchison to sell a minority stake in the combined entity to investors including the Canada Pension Plan Investment Board will not now proceed.
Explaining her decision to block the deal, Margrethe Vestager, the EC Competition Commissioner, said remedies proposed by CK Hutchison, including the sale of sufficient mobile spectrum to create a credible fourth player in the UK market, were inadequate.
“Allowing Hutchison to take over O2 at the terms they proposed would have been bad for UK consumers and bad for the UK mobile sector," she said.
Her verdict was backed by the UK communications regulator, Ofcom, and the Competition and Markets Authority, which had both lobbied against the merger.
Telefonica recently signalled that it would explore a sale or stock market listing of O2 if the Three deal was blocked.
A spokesman for the UK network said:
“The O2 business has continued to perform well in the market whilst the Commission process has taken place.
"Our customers are our priority and we will continue to differentiate, compete fiercely and remain successful, long into the future."
CK Hutchison has not ruled out legal action to try to overturn the EC decision.
Ofcom said:
“We believe this is the right outcome for mobile customers, who have always been our priority.
"Three and O2 are important and effective competitors in the UK, helping to deliver innovation, investment and competitive prices over many years.
"Competition must be sustainable, and regulation should support it.”