KFC was warned months ago that it could face delivery problems by using DHL, according to a union.
Many UK outlets are expected to be closed for the rest of the week, or will be forced to reduce menus and opening hours, due to a lack of chicken.
The poultry shortage is due to a delivery problem after the company decided to start using DHL as its deliverer rather than Bidvest Logistics in order to save money, The Guardian reported.
The GMB Union's national officer Mick Rix claims he told the company months ago there could be issues with deliveries using DHL, as Burger King previously had a similar problem.
He said: "I wrote to KFC. I alluded to Burger King trying to cut costs and ending up with poorer quality service and poorer distribution.
"They had shortages, too, but not on the scale we’re seeing now at KFC. Within six months they [Burger King] were pleading with Bidvest Logistics to take it back.”
He also claimed his sources believe KFC management knew "three weeks ago" there would be a huge problem with DHL and were worried about "the set-up and the systems after testing."
Rix added that some answers from DHL were "completely strange and worrying" following the testing and it was obvious the new system "was going to fall flat on its face.”
The national officer believes if KFC could go back to Bidvest "you could have a good operation up and running within a couple of weeks" as "DHL will not be able to provide the service they quoted for."
The move to DHL caused the loss of 255 Bidvest staff, a spokesperson for KFC has said: “We feel for those who lost their jobs at Bidvest; the decision to change supplier wasn’t taken lightly. DHL have estimated that winning the KFC contract and opening the new distribution centre has created 300 new jobs."
It is not clear when the fast food chain will return to normal operations, but the current problems have caused much public outrage.
Some have even called the police as the force in Tower Hamlets tweeted: "Please do not contact us about the #KFCCrisis - it is not a police matter if your favourite eatery is not serving the menu that you desire."