Tech giant Google has given its army of 'quality raters' around the globe a new tool to flag up content that might come across as "upsetting or offensive".

According to reports the "upsetting-offensive" content flag has been added to guidelines used by the search engine's global review teams in a bid to draw attention to potentially unsuitable content and help train Google's machine-learning systems to recognise unsuitable results.

The guidelines are said to include example searches to demonstrate the feature, including one for "holocaust history" which shows two conflicting results. One result which suggests the Holocaust "didn't happen" should be marked as "upsetting-offensive" and a second example result from The History Channel, classed as a "factually accurate source of historical information", should not be flagged according to the guidelines.

Google has not officially commented on the search guidelines update, but a senior engineer told industry blog Search Engine Land the company wanted to target "demonstrably inaccurate information."

Engineer Paul Haahr told the blog: "We're explicitly avoiding the term 'fake news,' because we think it is too vague.

"Demonstrably inaccurate information, however, we want to target."

Google uses data from global quality raters to help improve search algorithms - the raters themselves do not have the power to alter Google search results but flagging results gives the system more detailed information to work from.