Signal Media, a market intelligence firm, analysed 21,000 articles between the start of January and the end of March.
During this period, the 'leave' camp generated 1,654, or eight per cent, of articles that contained clear editorial supporting its messages, while 'remainers' generated 1,042 articles, around five per cent. The vast majority of articles (87 per cent) contained no clear support in either direction.
Prime Minister David Cameron and Boris Johnson, the outgoing London Mayor, have emerged as the key spokesmen for each side of the debate, with Cameron arguing to remain.
Signal Media’s data found Cameron had 165 mentions for the ‘remain’ campaign and 240 mentions about the ‘leave’ campaign, while Johnson had 67 mentions about the ‘remain’ campaign and 141 for the ‘leave’ campaign.
David Benigson, chief executive of Signal Media, said: "Recent history shows that using different types of media coverage can drive voters to the polls in higher than expected numbers. In fact, academics found that non-traditional media played a bigger role in the Scottish referendum than in any previous UK political campaign. With that in mind, I’d be surprised if we didn’t see an increased focus from both campaigns across all media in the final weeks."
The EU referendum takes place on 23 June. The designated lead campaign groups on both sides will be named next week.