The forward joined the Hoops in 2000 in a £6m (€10.5m) deal and went on to claim the domestic treble in his first season before playing in the Champions League and the UEFA Cup final in 2003.

But Sutton’s time at the club was soured after failing to agree a 12-month extension to his deal.

In a statement released through PA Sport, Sutton said: “I had five great years at Celtic under Martin O'Neill.

“I would like to thank the players and staff at Celtic for making me and my family so welcome. I would also like to thank the Celtic fans for their tremendous support.

“It has been very disappointing for me to leave Celtic but, under the circumstances, I felt that I had been left with no choice.

“I’m looking forward to playing for Birmingham City. Steve Bruce and Karren Brady could not have done any more to make me feel welcome and I’m looking forward to getting started for Birmingham City.”

Celtic boss Gordon Strachan expressed his disappointment at losing Sutton.

He told the club’s website, www.celticfc.net: “It is obviously a huge disappointment to lose a player of Chris’ quality.

“The club has granted Chris his wish to move on and I would like to wish him all the best for the future.”

Meanwhile, Preston manager Billy Davies continues to test the Hoops’ resolve over midfielder Stephen Pearson.

Strachan insisted the 23-year-old would not be leaving the club before the end of the season.

But the Deepdale boss has made an undisclosed bid for the player, while his agent, Willie McKay, has admitted Pearson would consider a move to the Coca-Cola Championship side.

Davies said: “We made the enquiry and now we’ve made the move. Maybe, with the appearances he’s made for Celtic, the opportunities may lie elsewhere and we’re hoping something can be done.”