Around half of the fast-food chain's 900 stores in Britain were closed Tuesday evening. Many of those still open are offering a reduced menu or have cut their hours.
Last week, KFC said the closures had been caused after it had taken on a new delivery partner, DHL, and apologized for the shortages.
A KFC spokesperson said the company anticipated the number of closures to fall over the coming days while they worked "flat out all hours to clear the backlog."
"Each day more deliveries are being made; however, we expect the disruption to some restaurants to continue over the remainder of the week, meaning some will be closed and others operating with a reduced menu or shortened hours," the spokesperson said.
Delivery firm DHL, which took on the contract last November with food service company QSL, said it "regrets" the interruption of supply and is working to rectify the situation as soon as possible.
"Whilst we are not the only party responsible for the supply chain to KFC, we do apologize for the inconvenience and disappointment caused to KFC and their customers by this incident," a DHL spokesperson said Monday.
KFC has set up a webpage for U.K. customers to find out the latest updates regarding their nearest outlets.