Highly-regarded striker Jack Marriott has signed a new contract with Ipswich until the summer of 2015.
Kris Commons says Celtic urgently need to find a top-quality striker to compliment their midfielders.
The 33-year-old striker signed a new one-year deal last summer under then-boss Paul Jewell but has only featured once off the bench since the appointment of Mick McCarthy in early November.
Scotland will now look to gain regular first-team football elsewhere.
McCarthy told Town's official website: "Jason is a fantastic guy and has been great around the training ground but we are going younger and he's been missing out.
"He understands that and wants to go out and play football at the twilight of his career. We wish him well."
Scotland joined Ipswich from Wigan in 2010 and enjoyed close to 100 appearances in total, scoring 21 goals.