Music
Julian Makey/Rex Features
In a band statement, Campbell said that he wanted to focus on his solo career.
The singer's last gigs with the group will be in Australia, New Zealand and Uganda next month.
A spokesperson for the band said: "Ali Campbell has taken the decision to focus on his solo career, and in doing so could not give his full commitment to UB40.
"The other band members of UB40 are naturally disappointed and saddened after being together as a band unit and as good friends and a family unit for almost 30 years.
"UB40 will continue to record and perform with the existing seven members."
The band's new album 24/7 will be released as planned.
UB40 have sold over 70 million records since they formed in 1978 and have had hits with songs such as 'Red, Red Wine', 'I Got You Babe' and 'Can't Help Falling In Love'.
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