The former football manager seemed to make a joke about Muslim women wearing burkas.
In scenes which aired last night (August 25), Danielle Marr placed her jumper over her head while in the garden.
After a small sing-song, Atkinson joked: "You're not carrying a bomb with you, are you?"
Big Brother summoned Atkinson to the Diary Room and he was given a formal warning as his remarks could be deemed offensive and inflammatory.
Ron Atkinson has previously expressed regrets over entering the house, saying: "I'd be quite happy to pack my bags and go. I now know this ain't my scene. I'm having to keep a lid on a lot of things…"
Celebrity Big Brother continues tonight at 9pm on Channel 5.