News organisations need to become "more inventive" to arrest a decline in traditional revenue sources, an international survey has warned.

Researchers at Oxford University found that digital subscriptions and online advertising were failing to compensate for the collapse in newspaper sales.

Fully 75% of Britons said they would never consider paying for online news.

Respondents also expressed frustration with so-called "sponsored content" being disguised as news.

The fourth annual Reuters Institute's Digital News Report, which is backed by Google, Ofcom and the BBC, surveyed the news consumption habits of almost 24,000 people across 12 countries, including the UK, US, Australia, Japan and Brazil.

Almost half of those questioned said they accessed news on a smartphone - a significant increase on last year's study - but revealed they were loyal to just one or two news sources on the device.