Mail Online has hit out at a US media start-up which ranks news websites for trust and credibility after it claimed the UK’s most-visited news site failed to uphold “basic standards of accuracy and accountability”.

New York-based Newsguard has created a free extension for Google’s Chrome and Microsoft’s Edge browsers that hands out “green” and “red” ratings to news websites based on their trustworthiness.

Its team of analysts handed Mail Online a red rating, the same as it gave to Kremlin-backed news websites RT (formerly Russia Today) and Sputnik.