The National Union of Journalists has cancelled its annual Black History Month lecture after its guest speaker this year, Canary editor Kerry-Anne Mendoza, published reports attacking a Guardian freelancer working in Nicaragua as part of a “smear campaign” that led to his deportation.

Goette-Luciak had been covering protests calling for Nicaragua’s long-serving president, Daniel Ortega, to step down. Hundreds have been killed in a violent government crackdown issued in response, which the NUJ says has also targeted journalists documenting the protests.

Goette-Luciak was described as a “novice reporter” who has “published pieces littered with falsehoods that reinforce the opposition’s narrative promoting regime change” in an article by Max Blumenthal republished by The Canary.

It had originally appeared on alternative news website Mint Press News, with Goette-Luciak described in the headline as “the MSM’s man in Nicaragua”. MSM is shorthand for “mainstream media” and is a popular term among left-wing news websites.

Blumenthal, also editor of online investigative outlet the Grayzone Project, claimed Goette-Luciak had “forged intimate ties to the opposition, and has essentially functioned as its publicist under journalistic cover”.

The article was published by The Canary on 28 September, despite a warning from non-profit press freedom group the Committee to Protect Journalists just three days earlier stating that Goette-Luciak was the victim of a “targeted online harassment campaign” and calling on authorities to “find those responsible and ensure his safety”.

The Austro-American reporter told the CPJ he had been living in Nicaragua for three years, working primarily as a documentary film before switching to full-time journalism around April this year to cover the “growing anti-government protests across the country”.

He is also director of investigations at La Ciudadana Radio, which has run coverage critical of Ortega’s government.

Goette-Luciak said he began receiving threatening messages on 16 September and that he believed people had tried to follow him home on multiple occasions before his address was posted online in a move known as doxxing.

On Monday Goette-Luciak was taken from his home by law enforcement officials and deported the same day. His father told the Guardian he had been interrogated, but was not hurt.

In a statement after his deportation, NUJ general secretary Michelle Stanistreet said: “Unfounded accusations against journalists of being spies, agents and terrorists are tactics used by repressive regimes throughout the world.

“Online smear campaigns designed to add to that pressure clearly serve to increase the risk and danger to all journalists working in already difficult environments.”

Yesterday The Canary published a second article about Goette-Luciak, claiming an exclusive interview with his “longtime friend” Wyatt Reed – again bearing Blumenthal’s byline.

Reed is reported as having said the two of them were assisting opposition groups in Nicaragua and that there was “a straightforward conflict of interest involved in what we were doing”.

The Canary also published a letter it said it was from Reed, “outlining his concerns about Goette-Luciack” to the Guardian, Washington Post and NUJ.

It reads: “I must be extremely clear: in the six months we lived and worked together in Nicaragua we were both very open about our plan to use our friendships with Nicaraguan opposition figures to push for the end of the Sandinista government and create careers for ourselves as journalists or consultants in the process.”

The Guardian has said it stands by Goette-Luciak’s reporting on recent violence in Nicaragua for the newspaper, adding that it will “continue to report from the country in a balanced and responsible way”.

The Canary was co-founded by Mendoza, who is also its editor. She has appeared on TV debates, including BBC Question Time, representing the website which came up along with the rise of Jeremy Corbyn.

It is arguably the most well-known of the so-called “alt-left” websites that typically support the Islington North MP.

Mendoza, who is mixed race, had been due to deliver the Claudia Jones Memorial Lecture for Black History Month on 11 October at The Guardian and Observer building in Kings Cross, London (where the newspaper is produced). The lecture is organised by the Black Members’ Council.

It has now been pulled, without a replacement venue having been found, and the issues surrounding the event look set to be debated at a meeting of the NUJ’s National Executive Committee on 12 October.

An email to staff from Guardian economics editor Philip Inman, shared by Buzzfeed UK’s Mark Di Stefano, about the attacks on Goette-Luciak said: “It is clear that the main source of intimidation was The Canary news website, which named Goette-Luciak as an opposition stooge – an accusation that quickly led to his arrest and deportation.”

Within the email, Stanistreet also said that “unsubstantiated allegations and online smear campaigns that serve to jeopardise the ability of journalists to do their work safely are wholly unacceptable and fly in the face of the NUJ’s Code of Conduct”.

The Guardian NUJ chapel committee has condemned The Canary’s actions along with the chapel’s black/BAME journalists, who said: “As minority journalists we believe the principle of solidarity with fellow journalists is crucial.”

The NUJ has confirmed that is has received a number of complaints relating to The Canary’s reporting, which are being followed up in accordance with the union’s rule book and code of conduct.

But press regulator Impress, of which The Canary is a member, said it has not received any complaints over either of its articles about Goette-Luciak.

The Canary told Press Gazette: “At the time Mark Di Stefano released this announcement, Buzzfeed had already been forced to retract the false allegation Guardian journalists used to pressure the NUJ into moving the lecture.

“Despite having the correction hosted on his own article, Di Stefano failed to mention it in this announcement.

“It is beyond irony that Westminster journalists are guilty of both charges they laid (falsely) against us.

“They are knowingly promoting a fake news narrative, and they are bullying a journalist. This lecture is about Claudia Jones. The Guardian tried to make it about themselves.”