A nagging back injury has forced Australia vice-captain Michael Clarke to quit the Champions Trophy in South Africa and return home for treatment.

Team physio Alex Kountouris said Clarke had been troubled by pain in his lower back since the recent one-day series in England and had been advised to take an immediate break.

"On arriving in South Africa the pain has intensified and he has not been able to participate in any of the team's training sessions," Kountouris said in a statement on Tuesday.

"He has received intensive treatment but it is apparent that he will not be able to take any part in the remainder of this series."

Australia have yet to decide on a replacement for Clarke.

They play Pakistan at Centurion on Friday needing a win to be sure of a place in the semi-finals.