Customers are threatening to boycott Groupon after an advertisement appeared on the website describing the color of boots as 'n***er brown'.

The racial slur was discovered on two pages on the deal retailer's site and caused immediate outrage on social media.

A third party Groupon vendor had listed two pairs of suede boots on the site with the color choices being apricot, black, brown and n***er brown.

Both pages and the vendor have since been removed.

Customers are threatening to boycott Groupon after an advertisement appeared on the website describing the color of boots as 'n***er brown'

Groupon issued an apology on Wednesday, saying it was appalled by the language used in the advertisement.

'This product description was provided by a third-party seller via our self-service platform. Regardless, this is completely unacceptable and violates our policies - to say nothing of our values,' Groupon said in a statement.

'When made aware of the issue, we immediately removed the deal - as well as the third-party seller - from our marketplace. Language like this has no place on Groupon, and we're further strengthening our self-service controls to ensure it doesn't happen again.'

The two boots on sale were 'Womens Mens Suede Leather Fur Lining Winter Boots' and 'Women's Fringed Suede Moccasin Boots'.

Twitter users bombarded the company with complaints and demanded an explanation over the racial slur.

'No way @Groupon no way!!!!! 'N****r Brown'???? REALLY!! And I'm tired of apologies from these blatantly racist organizations. THROW THE WHOLE BUSINESS AWAY,' one angry user wrote.

'I can't believe @Groupon has a woman's boot called 'N****r-Brown'. What type of color exactly is 'N****r-Brown'? another wrote.

Another user said: '@Groupon you have some explaining to do. New color choice selected by a racist employee? #shutdowngroupon.'