Most coverage of Muslims in British news outlets has a negative slant, according to a major analysis by the Muslim Council of Britain, which concludes that news stories in the mainstream media are contributing to Islamophobia.

The study found the Mail on Sunday had the most negative coverage of Islam, with 78% of its stories featuring Muslims having negative themes – above an already-high industry average of 59%.

The New Statesman, Observer and Guardian were the least likely to portray Muslims in a negative light, according to the analysis of 11,000 articles and news broadcasts during the final three months of last year.

The findings come amid growing scrutiny of Islamophobia in the Conservative party and whether its roots lie in rightwing media coverage. A YouGov poll of Tory members by the campaign group Hope Not Hate found that 60% believe “Islam is generally a threat to western civilisation” and more than half believe “Islam is generally a threat to the British way of life”.

Miqdaad Versi of the Muslim Council of Britain said he did not want to stop news outlets reporting on negative stories about Muslims but asked journalists to ensure that they considered the tone of their coverage. He also encouraged news outlets to include more positive stories about Muslims and not simply focus on terrorists and extremists.

“You need to ensure that when you write a negative story it is fair and reflective and doesn’t generalise about all Muslims and feed into a broader far-right narrative,” he said. “In addition to that there’s an issue of standing back and looking at all the stories out there and seeing if we’re reflecting all the stories. Are we only covering the worst Muslims out there?”

British television stations, which are regulated for balance by the broadcasting code, were substantially less likely than newspapers to portray Muslims in a negative light, with local television broadcasts particularly likely to feature more positive stories about Islam.

Versi helped to launch the Muslim Council of Britain’s new dedicated centre for media monitoring after his success in campaigning for better representation of Muslims in the British media. He has repeatedly won substantial corrections from newspapers over their reporting of Islam.

He said a tendency by news outlets to over-generalise – such as using a picture of a woman wearing a niqab to illustrate stories on Muslims – had a real-world impact. He said he hoped to use the findings to highlight the issue to newspaper editors who might not be aware of how their coverage was perceived by Muslims.

“The way that the media reports on Islam and Muslims plays a role in Islamophobia,” he said. “This is not about censorship, this is about transparency.”

The media monitoring centre will produce a quarterly report analysing all mentions of Muslims and Islam in the mainstream British media, with donors paying for full-time staff to carry out the work. Although the methodology has been vetted by external academics, the organisation admits that the classification of exactly what counts as an anti-Muslim story will ultimately be a subjective decision.

The first report is to be launched in the House of Commons on Tuesday night, with guests including the Daily Express editor, Gary Jones. In April Jones told the Guardian that the newspaper he took over last year had been Islamophobic, prompting him to change its editorial direction. The Daily Express website is run by a different team.

Versi said there had been notable changes at some outlets recently. “There has been movement in the right direction and the number of front pages of the Daily Express which are specifically about Muslims or migrants has gone down significantly.”