Mcoffins and Spencer's customers complained after the chain decided to throw away the free cookie that came with hot drinks at the cafes of the chain.
The university justified the decision by saying that it was trying to minimize food waste and that many people threw their biscuits in the trash.
But instead of praising the store's environmental data, customers reacted with outrage by social media.
One of them complained in Twitter: "Marx and Spencer, what about the stunningness of free biscuits in your cafes? Two different M & S cafes and no mines with my coffee."
Another added: "M & S gave you a little tea free cookie, but from late, my plate is naked."
M & S defended its decision and added: "The free cookie is still available, our customers just have to ask. It's an effort to improve food waste, as we've found that many customers do not eat biscuit. "
For those who want to enjoy oatmeal biscuits at home, the supermarket sells them in their food halls in packs of 22 for £ 1.
Consumer expert Sue Hayworth told Sunday's Mail: "M & S is caught between a rock and a difficult place. It saves waste by stopping to automatically discard free cookies, but it faces complaints from customers who moan that they can not get a free cookie. "
Marx and Spencer have recently been shot for plastic waste after they have distributed free toys to children.
Earlier this month, customers criticized the promotion that handed out miniature plastic versions of the 25 most crafted items that were turned into miniature collectors in a campaign called Little Shop.
One Twitter user wrote: "Can you explain? I saw that they can be recycled in baby benches, but why do you make them first? Stop using unnecessary plastic just to get sales! This is extremely disgusting and YOU MUST START. "
M & S responded that the company is "committed to reducing the use of plastic packaging and reusing or recycling everything we use".
He added, "All the collections at Little Shop are designed to last and work hard to ensure that about a quarter of them are made from a Forest Forest Stewardship Council (FSC) certified card. We have also ensured that all disposable packaging is made of paper rather than plastic. "