Nearly 600 Amazon employees are reportedly heaping pressure on their top bosses to cut ties with ultra-right-wing website Breitbart News.

Last month staff at the online retail giant sent an email to chief executive Jeff Bezos and senior vice president Jeff Blackburn with the heading: “Amazon Must Stop Advertising on Breitbart News”, according to CNBC.

The message reportedly included a petition opposing Amazon’s advertising on Breitbart, with 564 signatures.

It believed to have alluded to a confrontation that took place between a member of staff and Mr Blackburn about advertising on a site claimed “regularly publishes hateful and bigoted content”.

“What is it going to take for us to stop advertising on Breitbart News?” the employee reportedly asked.

Amazon is not believed to have a direct relationship with Breitbart but it does select the exchanges through which it buys ads, which implies that it would have a degree of control over how they are targeted.

Pressure on Amazon to stop advertising on Breitbart has intensified since the US presidential election in November.

A petition on campaigning website SumofUs calling for Amazon to ditch Breitbart News has garnered more than 500,000 signatures.

The world’s most valuable brands Show all 10 1 /10 The world’s most valuable brands The world’s most valuable brands 1st - Google Google replaced Apple as the world’s most valuable brand, with a brand value of $109.5bn, according to Brand Finance The world’s most valuable brands 2nd - Apple Apple’s brand value declined from $145.9bn to $107.1bn in 2016 The world’s most valuable brands 3rd - Amazon Amazon's brand value rose from $69.6bn to $106.4bn in 2016 Amazon The world’s most valuable brands 4th - At&t Of the 40 telecoms brands in the ranking, AT&T in 2016 overtook Verizon as the most valuable brand rising to $87bn from $59.9bn the year before The world’s most valuable brands 5th - Microsoft Microsoft's brand value rose marginally from $67.3bn to $76.3bn in 2016 The world’s most valuable brands 6th - Samsung Amazon's brand value rose from $58.6bn to $66.2bn The world’s most valuable brands 7th - Verizon Verizon's brand value inched up from $63.1bn to $65.9bn The world’s most valuable brands 8th - Walmart Walmart's brand value rose from $53.6bn to $62.5bn The world’s most valuable brands 9th - Facebook Facebook's brand value increased sharply from $34bn to just shy of $62bn The world’s most valuable brands 10th - ICBC ICBC saw its brand value rise to $47.8bn from $36.3bn. It was the most valuabe financial brand in the world in 2016 replacing Wells Fargo

Amazon did not immediately respond to The Independent’s requests for comment on the letter.