The New York Sun owner, Dovid Efune, has begun exclusive talks to buy the Daily and Sunday Telegraph for about £550m.

Efune, a former editor of the New York-based Jewish publication the Algemeiner Journal, made the highest bid to buy the newspapers last month.

The exclusivity talks will trigger a six-week process of due diligence, it is understood, to ensure he is suitable to acquire the titles.

The deal will be subject to scrutiny by the media regulator, Ofcom. It will consider public interest laws, which include the need for accurate presentation of news, free expression of opinion and – specifically for newspapers – a sufficient plurality of views and persons with control of ownership. Final approval will rest with the culture secretary, Lisa Nandy.

Efune, 39, has a range of financial backers including the asset managers Oaktree and the family office of the US hedge fund manager Michael Leffell. Efune had sought backing from the investment management firm Hudson Bay Capital but it declined the opportunity.

Efune said: “The Daily Telegraph and Sunday Telegraph symbolise the very best of world-class, independent journalism and a commitment to relentlessly seeking the public interest. This unique institution has a storied history as a pillar of the British press, dedicated to providing readers uninhibited, clear-eyed coverage of the most consequential issues of the day.

“As a lifelong newsman – variably as reporter, columnist, editor and now publisher – I believe strongly that these values, in general, are fundamental to the advancement of any journalistic enterprise. It’s with these principles that the Telegraph is best positioned for even greater success going forward.”

Efune’s remarks about the conflict in the Middle East, particularly the Israel-Gaza war, have prompted impartiality concerns among staff. He has previously said: “Facts: There is no famine in Gaza. There is no genocide in Gaza. 30,000+ civilians have not been killed. Israel doesn’t target innocent people.”

After Israel launched a major military offensive against Hamas forces in Rafah earlier this year, he claimed: “Extinguishing 80% of a fire helps no one. Israel needs to finish the job in Rafah. All the innocents of the region will be better for it.”

The views held by Efune, who was born in Manchester and built his media career in the US, have caused concern across the Telegraph newsroom.

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 are now alarmed by the political bent of the new frontrunner.

“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. What does his strong and vocally expressed support of the Israeli right mean for the safety of Telegraph reporters in the Middle East?”

RedBird IMI – a consortium backed by Sheikh Mansour bin Zayed Al Nahyan, the 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.

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