Online criticism of journalists has become a frequent occurrence during Donald Trump's tenure as US president. Now research made available online by an NYU master's student has revealed the full extent of Trump's anti-press tendencies.

According to the findings, the president has posted 990 tweets that have directly or indirectly attacked the media since July 2015.

Stephanie Sugars, who previously worked with the Committee to Protect Journalists, documented the tweets over an 18-month period after she became alarmed by Trump's verbal attacks on journalists.

Twitter has become an effective tool for Trump in combating what he sees as unfavourable or dishonest media coverage. Tweets which take aim at his critics are often shared thousands of times by his supporters.

To others, Trump's behaviour reveals an authoritarian streak and a unhealthy disregard for democracy.

"I took it on as a labor of love and hate, and I suffered through his tweets every few days to log them," Sugars told the Colombia Journalism Review.

"It seemed important to maintain a record of what has appeared to be a deliberate and sustained campaign to discredit the media as an institution."

Further analysis of Sugars's work by students at the University of Georgia reveals who has borne the brunt of Trump's attacks:

Of the 990 recorded anti-press tweets, 250 were specifically aimed at individuals. Former Fox News anchor Megyn Kelly came out as the most common recipient, while NBC's Joe Scarborough, a TV anchor who has questioned the mental health of the president, came second.

A further 350 tweets were aimed at organisations such as CNN and the New York Times, coming first and second respectively.

Fox News was the third most cited organisation, although these tweets came during the pre-primary and primary election phase, when Trump was jostling for position and airtime with a number of Republican candidates. Fox is now seen to be largely falling in line behind the president.

Trump also has some favoured words and phrases. Fake News, the now ubiquitous term that he brought into the mainstream this year, has been used over 140 times, while 'failing', a word he uses to attack publications such as the New Yorker, was used 100 times in tweets.

Taken into context, the figures reveal a sustained agenda to discredit and undermine those who attempt to scrutinise him, his critics claim.

"After you read them all," Sugars says, "you can't help but see Trump for what he is: a man running a perpetual campaign against the press."