The consortium of private equity firms lining up a bid for Auna, Spain's second largest telecoms company, could be forced to raise its offer by €3bn to €14bn ($18.2bn). It would rank Europe's largest leveraged buy-out, almost treble the previous record.

An investment banking source said €14bn would be a realistic target for shareholders to expect from the consortium, which includes Apax Partners, CVC Capital Partners, Blackstone Group, Providence Equity Partners and Carlyle Group.