NEW YORK (NYTIMES) - News publishers have long had a fraught relationship with Facebook. But tensions have become more public in recent weeks, with news organisations openly criticising the tech giant for new policies that they say are harmful to journalism.

The most recent salvo came on Thursday (June 14), when Mr Mark Thompson, the chief executive of The New York Times, accused Facebook of unintentionally "supporting the enemies of quality journalism" by using algorithms that can mischaracterise news as partisan political content.

Mr Thompson was speaking at a panel discussion in New York, which also included Mr Campbell Brown, Facebook's head of global news partnerships. Mr Brown defended a policy Facebook recently introduced in response to criticism over how its ad network was able to be manipulated during elections.

Mr Brown cited the importance of safeguarding elections and said that the problems with political ads were "something we are deeply concerned about. We hear you".

In criticising Facebook, Mr Thompson showed two advertisements that The Times had recently purchased on the platform. Both had been flagged as political.

One ad promoted a news article about President Donald Trump's summit with North Korean leader Kim Jong Un. By calling it political content, Mr Thompson said, Facebook was blurring the line between reporting on politics and politics itself.

The other ad was a promotion for The Times' NYT Cooking site, with a manicured image of a pistachio rose water cake. There was no indication why that had been labelled political content by the algorithm.

Tensions between Facebook and publishers have been building since at least January, when the social network changed its News Feed algorithm in a way that demoted content from publishers in favour of posts from a user's friends.

Executives like Mr Robert Thomson, the News Corp chief and longtime lieutenant of tycoon Rupert Murdoch, and Mr Jonah Peretti of BuzzFeed have consistently called for increased payments from Facebook - which, along with Google, has been gobbling up more of the online advertising revenue that publishers need to survive.

But the latest fight has more to do with the treatment of content than the economics of the media industry.

Last month, with public and political pressure growing over Facebook's role in the 2016 election, the company unveiled a policy that created a publicly searchable archive for ads that its algorithms deemed to be political.

In addition, Mr Mark Zuckerberg, Facebook's chief executive, said the company would start ranking publishers by their perceived trustworthiness.

"I don't want trust to be a popularity contest decided by users of Facebook," Ms Lydia Polgreen, the editor-in-chief of HuffPost, said at the panel discussion, which was held at Columbia University's Graduate School of Journalism.

The panel, moderated by Ms Emily Bell, the director of the Tow Centre for Digital Journalism at Columbia, also included Ms Erica Anderson of Google News Lab and Professor Rasmus Kleis Nielsen, the director of research at the Reuters Institute for the Study of Journalism, who presented the institute's annual Digital News Report.

Publishers have been vocal in their protests of being included in the same archive as political ads.

This month, organisations representing more than 20,000 publishers in the United States wrote to Facebook to object to the policy, and some outlets, like New York Media and the Financial Times, have vowed to suspend their paid promotions on Facebook if the policy is not changed.

Facebook has agreed to create a distinction between publishers' content and political ads, but it has not yet built a separate archive.

Moves like those have only inflamed tensions with publishers, said Mr Jason Kint, the chief executive of Digital Content Next, a trade group that represents entertainment and news organisations, including The Times, and who signed the publishers' letter last month.

"Facebook communicated poorly," Mr Kint said. "They have not built trust with publishers."

Although Facebook remains a vital outlet for publishers, its power has diminished. According to data from Chartbeat, an online analytics company, publishers' traffic from Facebook has declined about 15 per cent in the past year. At the same time, traffic from Google is up 20 per cent since last August.

During the discussion on Thursday, Mr Thompson sparred with Mr Brown, who was an NBC News correspondent and a CNN anchor before joining Facebook.

In response to his complaints about the ad policy, Mr Brown said there was a "fundamental misunderstanding" of the policy, adding that "The New York Times does not want to be transparent about the money they spend" on ads.

Mr Brown had written in a recent blog post that many publishers had welcomed the new policy. "I've yet to meet one," said Mr Thompson.

Mr Thompson also called Mr Zuckerberg's comments on trust "terrifyingly naive", echoing a speech he gave on Tuesday at the Open Markets Initiative in Washington.

In that speech, Mr Thompson accused Facebook of trying to "set itself up as the digital world's editor-in-chief, prioritising and presumably downgrading and rejecting content on a survey- and data-driven assessment of whether the provider is broadly trusted or not".