The email campaign by betting agent Boylesports, which features a a graphic picture of a hand nailed to a piece of wood, was sent out over the Easter weekend.
The attached message read: "In memory of the dearly departed JC, we are offering you a sacrilegious bonus this Easter weekend ... So don't just sit there gorging your own body weight in chocolate, that's disrespectful. Get on Boylesports Gaming and get your nailed on bonus."
Despite receiving just one complaint, the ASA felt the advert, and it's timing, was offensive to Christians.
In its ruling, it said: "We considered that the way in which the ad made light of the subject matter, with the play on words "NAILED ON BONUS"; the jokey language of "BETWEEN 5-25 QUID", "dearly departed JC" and "sacrilecious Bonus", and the cartoon-style image of blood dripping from the hand pierced by the nail, a particularly sacred image for Christians, were likely to cause serious offence to some recipients.
"We considered the offence was likely to be particularly strongly felt by those of the Christian faith at Easter, when the imagery would have a particularly strong resonance. We considered that the ad was likely to cause serious offence and concluded that it was therefore in breach of the Code."
Boylesports claimed the language and imagery associated with crucifixion had been absorbed into everyday culture and cited examples from film, music and everyday language therefore the advert was acceptable.
The ASA says the ad must not appear again in its current form and has told Boylesports to ensure future ads do not cause serious or widespread offence.