Staff at the Mirror, Express and Star newspapers lambasted executives and the CEO of their parent company during a live stream on Wednesday, after Reach announced plans to cut about 450 jobs – almost a 10th of its entire workforce.

Jim Mullen, the chief executive of the company, which also owns regional UK titles including the Manchester Evening News, Birmingham Mail and Liverpool Echo, faced a barrage of furious comments from editorial staff as he outlined plans to further slash costs at the UK’s largest commercial news publisher, part of proposals to trim operating costs by 5%-6% in 2024.

In comments seen by the Guardian, staff called on Mullen to resign, said he was a “liability” and likened the company’s treatment of staff to an “abusive parent”. Sources said they had never known such anger at the company, which has already made major job cuts this year.

Reach said 320 of the jobs going would be editorial roles, with the extra savings helping it to invest in boosting its online output.

“Our industry has a history of change and the future will undoubtedly involve yet more,” said Mullen. “That’s why it’s essential we set ourselves up to win, by making our operations suited to an increasingly fast-paced, competitive and customer-focused digital world.”

One anonymous commenter wrote during the online meeting: “You are not a CEO. You and your corporate execs are executioners! You have killed journalism.”

Another staff member said the last round of redundancies had shattered their mental health, while others said readers’ experience of ads online was damaging traffic.

A source said that during the live stream, which lasted for 12 minutes, the editor of the Daily Mirror, Alison Phillips, emailed her staff to say it had been a “tough day” at the Mirror. “I know I can depend upon you to show compassion and support for each other,” she wrote.

The National Union of Journalists (NUJ) said it was “dismayed” at the scale and timing of the announcement.

“Members will be understandably shocked at the scale of redundancies, particularly with previous rounds already withstood in recent months, and in the run-up to Christmas,” said Laura Davison, national organiser at the NUJ.

“Reach’s efforts to address economic challenges must not come at the expense of journalists, who fear for their job security and the impact on quality journalism only able to thrive with the experience and talent of staff.”

The publisher has said that it aims to keep compulsory redundancies to a minimum. The NUJ said it was still assessing the impact of the cuts on the publisher’s extensive local newspaper operation.

The company is battling against a slump in the online and print newspaper advertising market, with digital revenues hit by Facebook and other large media platforms moving to deprioritise news.

“We will be liaising with both our reps and the company to ensure the best possible outcomes for members at this immensely difficult time,” said Davison. “Reach must act in the spirit of genuine and meaningful engagement.”

Reach has already cut costs by up to 6% this year. In January it announced a reduction of 200 roles in a £30m cost-cutting drive after a slump in the digital and print newspaper advertising market.

Market conditions have continued to remain torrid; the value of Reach has slumped 30% over the last year, with its digital revenue strategy affected by large social media platforms, most notably Facebook, deprioritising news.

In its third quarter trading update, Reach reported a 13.7% drop in digital revenue as online page views slumped by 21% year-on-year in the first nine months. Total print revenues also fell by 6%, with income from newspaper sales and advertising declining.

The acceleration of the digital-first strategy is also expected to see the group’s remaining separate daily and Sunday newspaper operations – the Mirror, Sunday Mirror and Sunday People, Daily Express and Sunday Express – move closer to single seven-day publishing operations.

The company said in its latest financial update that it expected to make £95m in profits this year but remained focused on “driving efficiencies” and reducing operating costs.

In July 2020, Reach cut 550 staff, about 12% of its workforce at the time, in response to the Covid pandemic.

“Hard work over the last few years means we have established ourselves as a leading digital publisher,” said Mullen. “But there’s more to do and today is about organising our business to deliver against that challenge.”