Some stunned viewers have claimed they can hear the bungling burglar swear at Paddington Bear towards the end of the 90-second ad that was first unveiled on Tuesday morning.
Paddington mistakes the bearded burglar, who is wearing a red coat and red stocking on his head, for Santa and helps him in returning all of the pinched presents back to where they belong.
Some viewers reckon they can hear the bunglung burglar swear at Paddington
A number of viewers took to Twitter to say they thought they'd heard something very different
Scoffing the odd mince pie along the way, he innocently helps the thief embrace the true spirit of festive period and recognise the error of his ways.
The scene finishes with Paddington reaching into his red hat to pull out a signature marmalade sandwich which he hands to the teary-eyed crook.
The ad was unveiled on Tuesday
But rather than tell him "Thank-you little bear" as they embrace, some have claimed they can hear the burglar say, "F**k you, little bear."
Luce Valentine wrote on Twitter: "Just saw the M&S Christmas advert. When Santa hugs Paddington we thought he said "f**k you little bear" instead of thank you."
Other viewers also claimed that Paddington should really be calling him Father Christmas
While another shared: "In the M&S Christmas advert it sounds like 'santa' says 'oh f**k you little bear."
A third added: "That Paddington Christmas adverts so cute! But keep thinking he's saying "Oh f*** you little bear" every time he hugs him?!"
An M&S spokesperson said he's clearly saying the scripted "Thank-you", telling The Sun: "He's saying, 'Thank-you, little bear'. I think it's really clear. We wouldn't change the ad."