Rupert Murdoch’s online channel TalkTV is facing criticism after it did not disclose that a journalist who travelled to Britain in a small boat for a documentary was a Reform party member and activist.

The channel revealed the “world exclusive” this week, stating that the treacherous journey had made the former builder turned journalist Christian Drogan the first British man “to invade his own country”.

The documentary, Invading Britain: The Undercover Migrant Returns, was released on TalkTV’s YouTube channel. It showed a year-long effort to board a small boat and cross the Channel from France into England.

Small boat crossings are the most prominent campaigning topic for Nigel Farage’s Reform UK. Drogan’s story was picked up by other outlets including the Times, the Telegraph and the Sun.

However, TalkTV did not mention that Drogan had previously been clear that he is a Reform member who harbours ambitions of running for office for the party.

Appearing on Reform’s in-house podcast in June, Drogan said: “I’m a Reform party member. I attend my branch meetings. I would like to stand at some level … that’s my official tie with Reform.”

Mic Wright, the media critic who raised concerns about Drogan’s political background, said audiences should be given the full picture about the reporter’s affiliations, given he was pursuing issues that chimed with Reform’s agenda.

Wright said: “It is fair enough to go and do this activity, but he’s not being represented as what he is – which is a Reform activist. He is not being presented in his totality.

“If someone who was a member of the Labour party was on a podcast saying they were a Labour member … and then they went out and made a piece of media and an investigation that was machine-tooled to fit with the campaigning lines of the Labour party, Reform would say: ‘Well, this is ridiculous – this is Labour propaganda.’

“It is deceptive to the viewers, readers and listeners of these titles and broadcasters.”

The criticism was strongly rejected by Isabel Oakeshott, TalkTV’s international editor, who is married to Richard Tice, Reform’s deputy leader, and worked with Drogan on the documentary.

“This is a truly desperate attempt to find something negative to say about an exposé that is very uncomfortable for all those who keep making excuses about Channel migrant crossings,” she said. “There is nothing deceptive about repeatedly risking your life to establish the truth about the ongoing invasion of our country.

“It is, in any case, abundantly clear, in both the documentary itself and accompanying TalkTV coverage, that this groundbreaking investigation was led by me. My political links could hardly be more public. The extraordinary footage obtained by my colleague Christian Drogan speaks for itself. How he chooses to vote is his own business.”

Drogan said he had been motivated by “getting to the heart of the biggest issues facing our country”.

“I’m a working-class lad from the north of England, watching my country change before my eyes,” he said in a statement. “The camera doesn’t lie. Video footage and audio recordings used to evidence an investigation are about as pure as you can get when it comes to trying to find and document issues that others would prefer to hide and deny.”

Murdoch’s company News UK, which owns TalkTV, did not respond to requests for comment.

Drogan is part of a “citizen journalism” website called Watchman. He also posts material on social media and has previously appeared on TalkTV as a reporter who was on the ground during a riot in Belfast earlier this year.

In the wider coverage of Drogan’s channel crossing, only the Times appears to have mentioned that he was “a journalist who has campaigned for Reform UK”.

Appearing on TalkTV, Farage said Drogan’s claim that the crossings were “a national security emergency” was the “exact phrase” he had been using.

“These are aggressive, dangerous young males,” Farage said. “There are some who say: ‘Could some of them turn into a force within this country, perhaps even an army within this country’? I don’t think we’re there yet, but the risk remains.”