Google and Facebook have unveiled plans to curb fake news reports on their websites after they were widely criticised for profiting from lies and even faced claims they had helped swayed the US election results.

The internet giants have tightened their rules with the aim of preventing content producers from getting advertising revenue from false or misleading reports.

It comes after they faced growing protests for failing to take decisive action over the growing number of fake news reports being distributed through social media and search results.

Both companies were also accused of swaying the US election result by facilitating a huge surge in entirely false stories about the presidential candidates being shared online in the run up to the vote.

Researchers have found a vast underbelly of websites producing entirely false content which have apparently drawn in many credulous social media users.

Some are intended to promote political campaigns - such as news sites promoting the conspiracy theory that Hillary Clinton carried out a murder. Others are simply designed to be 'clickbait' which can draw in revenue from advertising placed alongside the content.

The problem is made even worse by a technique used by both Facebook and Google known as 'filter bubbles' in which they attempt to learn users' interests and promote content which they think they will like.

It means that people who rely heavily on social sites or google search for news may fail to get a balanced view of contentious or political issues.

And if they share one false news story, they are likely to see any more along the same lines, shoring up their belief despite there being no basis in the reports.

Facebook founder Mark Zuckerberg has denied claims that the social network played any role in influencing the election result, claiming that "99%" of the content on Facebook was authentic.

However there are reports that some staff at the social media network have set up an unofficial task force to combat the problem.

Facebook said that it was now updating its policy to restrict adverts from appearing alongside "misleading or deceptive" content - though this will not impact on fake news that is shared by users on their news feeds.

Meanwhile Google said it would restrict adverts from being placed on websites and pages that "misrepresent, misstate, or conceal information about the publisher, the publisher's content, or the primary purpose of the web property".