Celtic chief executive Peter Lawwell says that any extension would threaten the integrity of the competition.

BBC: SPL prepares for season extension

Lennon has since apologised on his club's website, where he was also criticised by Celtic chief executive Peter Lawwell.

BBC: Neil Lennon confronts the officials at Ibrox

"Peter Lawwell appears to be the chairman of the sporting integrity committee for the SPL, " said the Rangers manager of the chief executive.

BBC: Smith angered by Lawwell remarks

Meanwhile, Celtic's chief executive Peter Lawwell has returned from the Champions League final in Rome to step up the search for Strachan's successor.

BBC: Reid dampens Celtic speculation

There are legal problems in Scotland with that, but it's already being looked into in a feasibility study led by chief executive Peter Lawwell.

BBC: Standing up for the Old Firm

It led to a meeting between Celtic chief executive Peter Lawwell and his SFA counterpart, Stewart Regan, who had already promised an overhaul of the refereeing system.

BBC: Celtic call for referee Dougie McDonald's resignation