Concern is mounting across the Telegraph newsroom over the threat to editorial impartiality and influence, as the New York Sun owner, Dovid Efune, is poised to enter exclusive talks to buy the Daily and Sunday Telegraph.

British-born Efune regularly posts hardline views about the situation in the Middle East, sparking alarm among staff as it looks increasingly likely that he will become their new proprietor, having tabled a £550m bid.

The move to exclusivity with Efune, a former editor of Jewish publication the Algemeiner Journal, who acquired the digital assets of former print newspaper the New York Sun three years ago, is expected this week.

However, two sources that while Efune had tabled the highest bid, David Montgomery’s National World, which has held presentations with Telegraph management, had not officially been ruled out.

One source said that National World had “been told” that Efune was set to seal the deal.

“There’s real concern in the ranks over what Efune will do to our editorial stance on the Middle East,” said one newsroom source. “We’re already pro-Israel but people are worried he’s going to turn the Telegraph into his own personal propaganda sheet.”

In a series of posts last week on X, he said Israel would “decapitate” Iran’s leadership with “targeted strikes and close quarter assassinations … I’d expect the Ayatollah himself would be in the cross-hairs”.

Last year, Efune – who has described himself in the past as a “conspicuous Jew” – gave a speech at a gala in New York held by the Algemeiner, where he now holds the title of honorary chairman, where he told attenders that when it comes to the Israel-Hamas conflict there is a need to “fight with every report and headline”.

Telegraph staff had railed against the potential editorial ramifications of being taken over by a consortium led by the GB News co-owner Sir Paul Marshall, which did not submit a second-round bid for the titles, and now they are alarmed by the political bent of the new frontrunner.

“It is not a mainstream view in the UK that West Bank Arabs might be ‘resettled’, and a second Jewish state be established, as he has suggested,” said a second source at the Telegraph. “What does his strong and vocally expressed support of the Israeli-right mean for the safety of Telegraph reporters in the Middle East? The consequences for the Telegraph politically and financially could be grave.”

Steven Barnett, professor of communications at the University of Westminster, said that staff could expect Efune to flex his editorial muscle if he got the Telegraph deal over the line.

“For owners of media properties these days there are no constraints on them in terms of independence and impartiality,” said Barnett. “I think we can expect if Efune does buy the Telegraph that we will see his world vision, his perspective, particularly on the Middle East, on every page. You can see that the news agenda would become significantly skewed in his direction, I would expect a much more pro-Israel perspective.”

He added that UK newspaper proprietors had a long history of funnelling their own agendas into editorial output.

“That is really no different to newspapers owned by Rupert Murdoch, they reflect the Murdoch worldview and his vision,” said Barnett. “Or the Daily Mail and [owner] Lord Rothermere’s views.”

Barnett does not believe regulators will have grounds to block Efune if he is successful in buying the Telegraph.

“The regulations are about ownership and plurality, not politics,” he said. “I don’t see any reason why the deal would be referred to the CMA [Competition and Markets Authority] or [media regulator] Ofcom.”

RedBird IMI – the consortium backed by Sheikh Mansour bin Zayed Al Nahyan, vice-president of the United Arab Emirates and owner of Manchester City football club and the US investment firm RedBird Capital Partners – has been forced to sell the Spectator and Telegraph titles after the British government published legislation to block foreign states or associated individuals from owning newspaper assets in the UK.

It is understood that a “backup plan” where RedBird Capital Partners might continue to hold a small stake in the Telegraph was discussed in the summer but has been dismissed.

Last year, Redbird IMI acquired the right to own the Telegraph titles and Spectator magazine after the Barclay family lost control of the titles over unpaid debts to Lloyds Bank.

Last month, Marshall agreed a £100m deal to buy the Spectator and shortly after Michael Gove, the former cabinet minister, was named as the new editor.

Efune and the New York Sun have been contacted for comment.