Customers only get their hands on the treats and cakes after paying at the bakery’s East Ham store in East London.
It comes after a North London store recently locked its drinks fridges after a spate of thefts.
Sun Squeeze Team member and consumer champion Martyn James said: “What have we come to when the small things that make life worth living like cakes and doughnuts have to be hidden away just so opportunistic thieves don’t steal them ?
“It’s time to clamp down hard on these antisocial criminals who are making life worse for employees and spoiling things for everyone.”
Greggs did not respond to request for comment.
A member of staff from the Archway store, North London, where the drinks fridge is padlocked, told The Sun on Sunday: “Shoplifting happens every day here.
“The fridge is padlocked because they would just take bottles and sell them round the corner.
“They take anything that’s not nailed down.”