Violent Islamist extremists are three times more likely than far-right attackers to be described as terrorists in the media, according to an overview of more than 200,000 news articles and broadcast transcripts.

The research found Islamist attacks were linked to terrorism in 78% of news reports about the incidents, whereas those from the far right who carried out violent attacks were only identified as terrorists 24% of the time.

The study was carried out by Signal AI, which has built a database of news output to help firms monitor how they are covered in the media. The company analysed news reports about 11 different terror attacks that took place in the last two years, plus transcripts of TV and radio broadcasts in 80 different languages, to identify a consistent reluctance by media outlets to describe far-right attackers as terrorists.

“Reporting on Islamic extremist attacks is quantifiably different to reporting on far-right attacks,” the company concluded, amid warnings from British authorities about the growing threat of far-right terrorists.

They found the media was unusually willing to label the far-right attacker who targeted two mosques in Christchurch, New Zealand, last month as a terrorist. Signal suggested this could be due to the decision by the country’s prime minister, Jacinda Ardern, to brand the incident an act of terror within six hours of the incident, which caused media outlets to swiftly follow her lead.

By comparison, other world leaders such as Donald Trump have been more reluctant to brand some comparable incidents – such as the October 2018 attack on a Pittsburg synagogue – as acts of terror, which in turn resulted in the media being reluctant to apply the term. Labelling individuals as terrorists has always been a controversial decision, with politicians often inconsistent in how they distinguish between a generic attack and an ideology-motivated act of terror.

“The Christchurch shooting is actually exceptional in how willing the media were to label the shooter a terrorist,” concluded Signal, suggesting media reports tend to follow decisions made by political leaders. “The reasons for this are not entirely clear but seems to have been added to by Ardern’s bold and immediate stance on the attack. If this is the case, it shows that influential figures may have the ability to shift the narrative around events and topics. Spokespeople’s language filters into the media and, likely, into public dialogue.”

Signal’s methodology involved comparing the number of news reports which mention an attacker alongside the words “terrorism”, “terrorist”, “terror” or “suicide bomber”, compared with the number of reports that name an attack but fail to mention any of those terms.

Signal found that TV and radio outlets were less likely than websites and newspapers to brand incidents of any variety as acts of terror, possibly due to the comparatively short length of broadcast news bulletins. The Guardian’s parent company has a small stake in the company through its GMG Ventures investment arm.

The data could be skewed by the widespread use of news agencies, which means many news outlets run near-identical stories based on the same original reporting, amplifying a handful of early editorial decisions made shortly after an attack. In addition, the media monitoring database used by Signal is only 15 months old, meaning it is relying on retrospective reporting when considering how the media describes incidents that occurred in 2017, such as the Manchester Arena bombing by an Islamist extremist and the far-right attack on a Quebec mosque.

However, Ben Moore, the Signal analyst who carried out the study, said no matter how the issue was analysed and which set of news sources were used, the overall pattern remained that Islamist attacks are substantially more likely to be branded as acts of terror than attacks by supporters of far-right causes.

“The trend was so consistent,” he said.