London (CNN Business) McDonald's (MCD), KFC (YUM) and Pret a Manger have joined with UK supermarkets to warn that crashing out of the European Union will result in "significant" disruptions to their supply chains.

The companies said in a letter sent to UK lawmakers on Monday that they will not be able to maintain the "choice, quality and durability" of food if Britain leaves the bloc without an exit agreement in place that protects trade with Europe.

"While we have been working closely with our suppliers on contingency plans it is not possible to mitigate all the risks to our supply chains," they wrote.

In addition to the fast food makers, the letter was signed by representatives of most of the country's biggest supermarket chains and the British Retail Consortium.

The United Kingdom is scheduled to leave the European Union in just 60 days. But UK lawmakers have rejected the exit deal negotiated by Prime Minister Theresa May, and companies are worried about a disorderly Brexit.

UK supermarkets are warning of dire consequences should Britain crash out of the European Union.

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