Former Labour Leader Ed Miliband and Vince Cable have called for Rupert Murdoch’s proposed takeover of Sky to be blocked band referred to the regulator Ofcom.

21st Century Fox has launched a second bid for the 61 per cent stake of British TV and internet provider Sky that it does not own, after a previous attempt was thrown out in 2011 in the wake of the phone hacking scandal.

In a joint article in The Observer, Mr Miliband and former Business Secretary Vince Cable wrote: “The question as to whether 100 per cent ownership is right now when it was not four years ago can be answered emphatically: no. James Murdoch, despite what the 2012 report said, is now back as chairman of Sky and is chief executive of 21st Century Fox as it seeks to take over Sky. There are crucial – unanswered – issues around the culture and competence of what went on at Murdoch-owned newspapers which have not been satisfactorily resolved or answered.

“The Murdochs may claim that editorial independence could be guaranteed by ringfencing Sky News, and impartiality protected by Ofcom, the regulator. But the answer to this and the deeper questions at the heart of this bid depend on trust and the conduct of the Murdoch organisation and family does not inspire trust. If it was inappropriate for the Murdochs to take 100 per cent control of Sky even before the multiple convictions of their former employees, it must be inappropriate now.

“Promises that might be made to the regulators that there will be a specified proportion of independent non-executive directors cannot overcome the reality of total ownership and control.”