A sign-making firm was "inundated" with abuse and threats after being wrongly blamed for creating posters at Sunderland's Stadium of Light, it says.
Jonathan Cawthorn said his Gateshead-based firm, Jonsigns, had been mistakenly named on social media as creators of controversial signs ahead of the Wear-Tyne derby last Saturday.
Sunderland owner Kyril Louis-Dreyfus apologised for the "serious error in judgement" regarding the posters.
Mr Cawthorn said the business had been targeted with malicious calls and messages, while dozens of negative reviews were posted across several websites.
"We got a lot of messages on our socials calling us different names, scum and threatening messages about the company," he told the BBC.