The men would each eat five bowls of stir-fry during their regular meals at the Mongolian barbecue, which invites guests to create their own dishes from the buffet. Diners are told they can request meals "as many times as you wish" for £12.
The manager, who did not want to be named, said the two friends were eating him out of business. He said: "Basically they just come in and pig out. We have put up with them for two years but I've had enough.
"They are in such a hurry to beat everyone to the food they spoil everything. We are supposed to be a buffet but they eat everything out of the bowls before people can get there. We just can't keep doing this."
He said diners drank only water and never paid the optional service charge. He added: "We are not a charity, we're a business. It's our restaurant and we can tell people not to come back if we don't want them to."
"We've been eating there for a couple of years then suddenly the owner came to our table in front of all the customers and went absolutely mental. He said we were a couple of pigs and we were banned for life. I couldn't believe it."