Facebook, Google and Twitter face the threat of new taxes to combat fake news, amid warnings the phenomenon is putting democracy at risk.

Leaked reports suggest MPs will call for a major clampdown on the social media giants to protect the West’s democratic processes.

The culture, media and sport committee, which has conducted a lengthy inquiry into fake news, is expected to call for social media firms to be made legally liable for harmful and illegal content on their platforms.

Facebook, Google and Twitter face the threat of new taxes to combat fake news, amid warnings the phenomenon is putting democracy at risk.

It is also expected to propose a levy on the firms to raise funds for combating fake news, and say social media and data protection lessons should be on the national curriculum.

MPs are expected to accuse the internet giants of acting ‘irresponsibly’ over what happens to the data collected by their sites. And they will warn that people’s behaviour is being ‘modified and changed’ by the content on social media sites, in an environment where there is little regulation.

What is expected in the clampdown on social media giants? All online political material should include information on who paid for it

The Electoral Commission should be given powers to impose substantially higher fines for breaches of election law than the current £20,000 limit

Social media firms should be made responsible for the content on their platforms for the first time

Regulators should carry out an audit of all social media advertising to assess its accuracy.

The committee is expected to warn that social media is being used to manipulate people’s views in a wide range of fields, including spreading ‘messages of hate’ Advertisement

The committee is also expected to criticise social media firms for ‘time and again’ refusing to co-operate with the authorities, saying they should no longer be allowed to ‘mark their own homework’.

But the report is set to spark a major row with Brexit campaigners, whose activities on social media are likely to come under scrutiny. Former Vote Leave chief Dominic Cummings, who is set to be criticised for failing to give evidence on his campaigning techniques, last night launched a pre-emptive strike.

Mr Cummings leaked a draft version of the report on his website and rounded on the MPs behind it, who he described as ‘charlatans’. He said the report ‘knowingly or incompetently makes false claims’.

MPs are set to warn that the ‘relentless targeting of hyper-partisan views, which play to the fears and prejudices of people in order to influence their voting plans and behaviour’ pose a serious risk to democracy.

The social media giants are set to face criticism for trying to ‘hide behind’ claims they have no role in regulating the contents of their sites.

Concern about fake news has spread in recent years. US campaigners have accused Moscow of spreading disinformation on social media in a bid to boost Donald Trump’s election campaign, while the United Nations has accused Facebook of being responsible for inciting hatred against the Rohingya minority in Burma.