An admission from manager Gordon Strachan at the club's agm that he viewed the attacker as 'unfinished business' before his departure for Aston Villa almost a year ago only served to stoke the fire further.
"It's a bit mischievous when people keep saying these things," he told the Daily Mail.
"I don't know the context of what Gordon Strachan said, but he has never spoken to me or to Shaun about it. This kind of thing goes on in football all the time, but it's just stirring up the same old story that has been going on for a year.
"It would be unsettling for anyone to have these things cropping up all the time. If anyone has a serious interest in the player, then they should show their hand - otherwise it's just speculation and mischief-making.
"I had people calling me up three months after Shaun left Celtic saying: 'He's coming back to Glasgow, isn't he?'
"Until there is an agreement on all sides, then he is not. And right now nothing is happening. If Celtic want the player, they have to go through the correct channels, club to club, then we will talk. But I have no plans whatsoever to talk to Martin O'Neill about the player."