THE Oxford dictionaries word of the year in 2016 was post-truth, an adjective defined as “circumstances in which objective facts are less influential in shaping public opinion than appeals to emotion and personal belief”.

Unfortunately, post-truth, which largely boils down to heart versus head, goes hand-in-hand with another of 2016’s favourite phrases: fake news.

Until recently, there was real news and lies. Fake news has blurred that distinction. It has made people question everything they read, see and hear.

How big a problem is it? Well, the FBI believes fake news played a role in the outcome of the US election. It doesn’t get much bigger than that.

Social media’s incredible reach makes it easy to propagate fake news. Sometimes a flippant remark can take on a life of its own with tweets and posts criss-crossing the globe until fake news becomes real news.

How does this happen? Because fake news is given the same prominence as real news by social networks. Why? Because nonsense produces more shares and engagement.

At the weekend, Dr Damian Tambini, director of the London School of Economics’ media policy project, said that Facebook, Twitter and Google should involve civil society, regulators and experts to “give some legitimacy and reassurance” to their information.

While politicians contemplate bringing in laws to make the printed press pay the cost of legal action against them, regardless of a complaint’s merits, social media has washed its hands of responsibility for fake news.

Social networks must shoulder their editorial responsibilities, in the same way our journalists have to source and verify their information. The Commons Culture Committee is set to summon social media chiefs to Parliament for an inquiry. It needs to get a move on.