Negative coverage of the European Union almost doubled between Britain’s last referendum on membership in 1975 and David Cameron’s pledge to hold a second referendum in 2013, a study has found.

Some 24 per cent of news about the European Community was negative in 1994, in contrast to 45 per cent in 2014.

The research, which analysed 16,400 newspaper articles across five periods when the European Union was highly prominent in British news, also found that the most significant shift was the collapse in positive news about the European Union, which fell from 25 per cent in 1974 to 10 per cent by 2013.

Five papers – the Daily Mail, the Financial Times, the Guardian, the Daily Mirror, and the Times – were categorised in terms of their reporting of the EU, which was classified as either positive, negative, mixed or factual.

Coverage was sampled in five periods: 1974-5 when the first referendum was held, 1985-6 during the negotiations and agreement of the Single European Act, which created the single market, 1991-2 during negotiations on the Maastricht Treaty, which split the Conservative Party and birthed modern Euroscepticism, 2001-2 during the Nice Treaty negotiations, and 2012-3, when David Cameron made his referendum pledge.

Paul Copeland, who co-wrote the study with Nathaniel Copsey and lectures in politics at Queen Mary University, said the most significant finding was that there were “no real defenders of the EU to be found” in 2013 as opposed to 1975, while there was a “significant increase” in negative coverage in the right-wing press. “The only counter-weight to the noisy and negative minority is factual and neutral reporting: good journalism, but not necessarily effective as a spirited public defence of the EU.”