An undercover investigation of a dairy farm has prompted British high street giant M&S to sell only RSPCA Assured milk.
The footage taken by leading international animal organization Animal Equality uncovered potentially illegal - and cruel - practices on one of M&S's Dorset farms.
Images showed large calves kept in cramped conditions in tiny pens - potentially a breach of welfare regulations.
At the time, M&S Food Director Andy Adcock, said: "We hold our hands up. Keeping calves over eight weeks old in such pens is unacceptable. One of our farmers made a mistake."
Clive Brazier, Head of RSPCA Assured, said: "For the first time ever, consumers will be able to buy RSPCA Assured labelled milk in a high street retailer.
"This is a major step forward for improving dairy cow welfare and we hope other retailers will follow suit."
Speaking to PBN, Animal Equality's Executive Director Toni Shephard, said: "We are pleased our groundbreaking investigation prompted M&S to audit standards on its farms.
"We hope the RSPCA assurance will prevent calves from suffering in tiny pens beyond the legal age limit."
But increased welfare standards will not remove the cruelty from the dairy process, according to Shephard.
She added: "However, newborn calves will continue to be removed from their mothers - this is an unescapable part of milk production and can only be avoided by choosing one of the may plant-based milks available."