The 22-year-old is out of contract in the summer and the Fir Park club had hoped to convince him to sign a new deal to remain in Lanarkshire.
But manager Graham Alexander has revealed on Tuesday morning that one final attempt to get the midfielder to pledge his future to the club has failed.
Campbell has previously been linked with a move to Hibs and Scottish Premiership rivals Aberdeen. However, a £500,000 development fee Motherwell would be due in compensation is likely to make him too costly for any Scottish side outwith the Old Firm.
Despite his tender age, Campbell has already racked up 159 first-team appearances, scoring 16 goals. He’s also been capped 24 times for Scotland’s under-21s.
English Championship side Millwall previously showed an interest in the player but decided to turn their attentions elsewhere.