In the statement the club claim to be 'extremely disappointed in the events that have led to his (Colback) departure' from the club.
Colback was born and raised in Killingworth, North Tyneside and completed a move to his boyhood club Newcastle United on a free-transfer after his current deal on Wearside expired.
In the statement issued by Sunderland, the club claim to have done everything in their power to ensure Colback remained at Sunderland. They also claim to have been misled by Colback and his representatives regarding extending the midfielder's time at the Stadium of Light.
The official statement read: “This wasn’t about money - the club agreed to all of the terms demanded of us during discussions and we were always led to believe that Jack wanted to stay with us. At his and his representatives’ request, final talks were put on hold until the club secured its top flight status. To our dismay however, we were subsequently never given the chance to negotiate with him to stay.
So from an official Sunderland stance it appears that Colback has turned his back on the club in favour of a controversial move to their fiercest rivals.
This is a move that will come as a surprise to some fans of both north east clubs who had witnessed the 24-year-old exuberantly celebrate his goal in Sunderland's 3-0 derby victory over Newcastle at St James' Park.
The midfielder's derby antics are famous in the north east and have resulted in some Newcastle fans being reluctant to welcome their new signing with open arms.
Many Mags had taken to Twitter today to express their distaste for their new signing, but tonight's statement from Sunderland might go some way to endearing Colback to his new fans.
The statement ends: “For him to then leave the club that has supported him throughout his formative years in such a manner, with no chance for Sunderland to recover any of the significant investment that it has made in him as a player, has left a bitter taste."