The BBC has said it will cut 450 jobs from its news operation and cover fewer stories as part of an effort to save £80m, as executives warned that the corporation is facing an unprecedented threat to its future.

The head of news, Fran Unsworth, announced on Wednesday that journalists at the corporation would increasingly be pooled in centralised teams rather than working for specific programmes, with an increased emphasis on its online output rather than its television and radio stations.

Newsnight, Radio 5 live, the World Service’s English-language output and the Victoria Derbyshire programme will be among the worst-affected stations and shows, although the impact will be felt across the board with management still deciding where hundreds of redundancies will fall.

Unsworth said the corporation was covering about 100 different news stories a day across all of its output, and this was “overwhelming” the public and many stories were not reaching their intended audiences.

The news operation is required to make annual savings of £80m by 2022 but is only halfway to this target, leading to this round of redundancies. Unsworth said potential decriminalisation of non-payment of the licence fee, being considered by the government, could result in further cuts.

“Producing fewer stories means we have to be a smaller organisation,” she told staff, emphasising the BBC was under attack from changing media habits, claims of bias and threats to its funding.

An image of BBC News’s future commissioning structure, from a presentation given by Fran Unsworth. Photograph: BBC

“Never in my career have I felt this organisation is quite under the threat that it currently is. There are many that believe that how we are funded is no longer appropriate when consumers seem to prefer to pay just for what they use.”

In addition to the already announced axing of the Victoria Derbyshire show, there will be heavy cuts at Newsnight. The programme will lose a dozen posts, production of its in-depth films will be halved and its spending on investigative journalism will be reduced. Staff at the programme fear this will increasingly leave it reliant on studio-based discussions.

According to the National Union of Journalists, which said the BBC was facing an “existential threat”, a dozen jobs will go at 5 live, while the sharing of radio bulletins across the BBC will result in a further 12 job losses. There will also be an effort to reduce the number of on-screen news presenters, with five positions at risk.

Fran Unsworth: ‘Producing fewer stories means we have to be a smaller organisation.’ Photograph: Jeff Overs/BBC

Unsworth told staff: “I do need to be honest with you: this organisation has to face up to the changing way that audiences are using us. We have to adapt. We need to create a modern newsroom that is built for the future and not for the past.”

A key part of this will be reducing the number of stories produced by the BBC and then sharing them across multiple outlets – meaning the same reporter could produce a report on the same story for radio, television and online rather than being sent by an individual show.

In an occasionally testy meeting of BBC News staff, Derbyshire accused Unsworth and other leading news executives of lying, regarding previous reassurances given about the future of her eponymous programme. The presenter said bosses had repeatedly praised her team’s journalism, the show’s ability to reach diverse audiences, and its performance online, only to close the show because it performs poorly among live TV audiences.

“It feels like you have changed the goalposts in order to justify closing our programme,” said Derbyshire.

Unsworth said traditional TV and radio station audience numbers were falling and the online audience was not making up the difference. At the same time, different BBC programmes were sending multiple teams to cover the same story in different ways.

“I understand why programmes want to make distinctive content simply for their audiences. But a modern newsroom needs to work smarter. We need to collaborate more and put the BBC News brand first,” she said.

She emphasised that the BBC needed to increase its online audience if it wanted to justify charging the £154.50 licence fee to under-35s who have largely abandoned traditional television news bulletins, even if it was opposed by commercial publications. “If the press don’t like it and the Sun don’t like it, well, I’m sorry, that’s just tough.”

She said the cuts would go through in their current form even if there was political opposition. “If we don’t stick to our guns, the BBC will run out of money,” Unsworth said.