An invited reviewer can have a co-reviewer on a manuscript as long as the journal’s editorial office is made aware of this and approves the co-review. The invited reviewer will need to reach out to the journal’s editorial office about the co-reviewer when they accept the review. The co-reviewer must also declare any relevant conflicts of interest.
The co-reviewer must be specifically identified during the completion of the review, either in the ‘Confidential Comments to the Editor’ section or, if a journal has a specific question about co-review, in the reviewer report form. This allows the co-reviewer to be credited for the review and to be added to a journal’s reviewer pool.
All journal reviewers must follow the COPE ethical guidelines for peer reviewing at all times. Please see the additional Cambridge guidelines for peer review: A Guide to Peer Reviewing Journal Articles