McCann, 32, who was Posh captain, was not expecting to leave the club this sumer.
"Just to clarify, no i did not ask to leave! Im in shock as much as anyone. Thank you for all the lovely tweets, but thats Football," he wrote on the social network site Twiter.
The Northern Ireland international scored eight goals in 47 appearances this season.
Hewas arrested on Wednesday for drink driving. He is due to appear at Peterborough Magistrates Court on May 10.
"Drink-driving is a very serious offence and there is no excuse for what I have done," said McCann.
"I will accept my punishment and I am extremely remorseful for what I have done."
McCann joined Posh on a Bosman transfer in May 2010, after turning down an extension to stay at Glanford Park.
He had been signed by then Iron manager Nigel Adkins in January 2008, witht he club paying Barnsley an undisclosed fee for the player.