The retailer faced calls on Facebook for customers to boycott the chain after a Muslim checkout worker allegedly told a customer they could not serve them Champagne on religious grounds, and that they would have to wait for a colleague to become free to process the transaction.
A Marks & Spencer spokesperson said its policy was to aim to meet staff requests not to work in departments where doing so would come into conflict with their faith.
The spokesperson said: "Customer service is our number one priority. We regret that in the highlighted case this was not delivered to our usual standards. We would like to apologise for any resulting confusion and reassure our customers that this was an isolated incident.
“M&S offers an inclusive, secular environment for employees and customers, working closely with any employee with religious beliefs of any denomination that restrict specific food or drink handling.
“We aim to manage this so that all employees work in departments that allow them to offer great customer service at all times.
“Requests are considered on a case-by-case basis and may lead to an individual working in a department where conflicts wouldn't arise, such as in clothing or bakery in foods.
“This policy has been successfully implemented over many years and does not compromise our ability to offer the highest level of customer service.”