Piccadilly Radio is a subsidiary of Trans World, which is currently the subject of a bid from Emap, the publishing group.
The offer is believed to have been made around the time Mr Oyston first considered selling his stake to Emap at 181p a share, a move which triggered a pounds 70m takeover bid for the whole company. Next week, the Guardian Media Group, which owns 20 per cent of Trans World, goes to court to try to block the bid.
Sir Bob said: 'I was asked to ring Mr Oyston and say that, in the event of him not coming to terms with Emap, there were people who would be interested in buying his shares.
'It was quite clear there was nothing to be gained from the conversation,' he added. Mr Oyston is believed to have preferred the Emap offer, believing it was the best chance for him and other shareholders to exit from the company.
Some shareholders believe that Sir Bob was acting on behalf of certain Trans World directors who are doing all they can to scupper the Emap bid.
Sir Bob declined to comment on who he was acting for, saying that the call was private.
Radio in step, page 6