Starbucks embarked on a Christmas campaign on Twitter at the weekend which was played out on a big screen in the Natural History Museum, where the coffee chain is sponsoring the ice rink.
Starbucks asked fans to tweet using the hashtag #spreadthecheer. The messages were then were blown up onto the giant screen.
Unfortunately the filtering system crashed, allowing those critical of Starbucks' tax bill, or lack of it, to flood the feed with less than complimentary messages. One tweet called Starbucks "tax dodging MoFos", while another simply said: "Hey Starbucks, PAY YOUR F**KING TAX".
Another Twitter user encouraged customers to tip staff "as Starbucks has just cut their wages", while another wrote: "If firms like Starbucks paid proper taxes, Museums wouldn't have to prostitute themselves to advertisers."
The National History Museum apologised for the mistake and said that sponsorship deals such as the one with Starbucks helped the museum to put on extra events.
A Starbucks spokesman said: “We apologise to any visitors who may have been offended by inappropriate messages displayed on the Twitter wall screen at the Natural History Museum’s ice rink café. This was due to a temporary malfunction with the content filtering system."