One case taken up recently by the Equality and Human Rights Commission concerned a website, keepcalm-o-matic.co.uk, through which customers can create their own variations on the slogan "Keep Calm and Carry On".
When the commission was alerted to examples such as "Keep Calm and Burn Jews", it wrote to the company to ask for their removal.
Aidan Fitzpatrick, director of Keep Calm Network Ltd, said the company was "very sorry to see this abhorrent content uploaded to our site" and had removed it.
He added that the site had "the capability to automatically block posters with specific words or phrases and we have added the phrase you highlight to this mechanism".
All orders for goods, he said, "get vetted and content such as this would not get through the process."
Mr Fitzpatrick acknowledged that some variations of the phrase could get through the blocking process.
He added: "We can certainly look to add additional phrases to the blocklist.
"It's an ongoing task.
"As you will imagine there is a large and growing body of hateful things that people might write."
Examples found by the JC on the website this week included the slogans "Don't keep calm and run from the Jews!!!" and "Keep calm and burn Jewish".
The slogans were removed after the JC alerted the company.
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