Embattled Toronto Mayor Rob Ford has said he cannot guarantee he will stay sober if he is re-elected, telling a radio show people will have to trust him.

Ford, who returned last week to the city council from two months in rehab, said in a radio interview he cannot make promises about something over which he has "no control". Ford said earlier he has used cocaine, marijuana and hallucinogenic mushrooms.

He said in April he would seek help for alcohol addiction after a video apparently showed him smoking crack cocaine.