Be honest
Whatever you decide, be truthful with your colleague about what you’re willing to do and say. If you feel you really can’t serve as a reference, say so, says Glickman. She recommends declining this way. “Say, ‘I am not going to be able to give you a strong enough recommendation. You need someone who can really sing your praises.’” If your appraisal of the candidate’s abilities is mixed, Claman advises having a “conversation [with the applicant] about what exactly you might say” to a reference checker. Be candid, but diplomatic about the particulars. “Say, ‘I could give you a reference about how well you deal with customers, but I can’t give you a reference that includes your ability to stick to a budget.”