Prezzo is to shut 46 loss-making restaurants, including five in London, after being hit hard by soaring energy and food costs.
The Italian restaurant chain has said about 810 workers are at risk of redundancy as part of the overhaul.
Bosses at the private equity-owned businesses said the cuts, which are part of a broader strategic review, will affect sites where “the post-Covid recovery has proved harder than we had hoped”.
The closures include five in London - in Chingford, Eltham, Mill Hill, Sidcup and Woodford Green.
Meanwhile, a number of restaurants just outside London will also close, including in Brentwood, Buckhurst Hill, Egham, Epsom, Harpenden, Redhill, Shepperton and Weybridge.
The shake-up will leave the hospitality chain with 97 restaurants and about 2,000 staff.
It said the closures will impact some high street sites as its portfolio shifts more towards those “in better locations to cater to changing consumer habits” such as shopping centres, retail parks and tourist destinations.
Staff were informed about the closures on Monday morning, with a consultation process launched.
Prezzo said it will work to redeploy “as many staff internally as possible” and will support others in new opportunities.
The restaurant group said costs have leapt over the past year, with its utility bills more than doubling and double-digit wage inflation.
It has also been impacted by soaring food inflation, which hit a 45-year high last month, with Prezzo witnessing a 40% increase in the cost of spaghetti, 28% rise for pizza sauce and 15% increase in the cost of its dough balls.
Dean Challenger, chief executive of Prezzo, said: “The last three years have been some of the hardest times I have ever seen for the high street and I’m extremely proud of the way our colleagues have retained Prezzo’s position as an appealing, trusted, great value food and drink experience.
“But the reality is that the cost-of-living crisis, the changing face of the high street and soaring inflation has made it impossible to keep all our restaurants operating profitably.
“We believe the tough decisions we are making today will ensure Prezzo can continue serving communities with high-quality, accessible Italian-inspired meals for many more years to come.”
The hospitality firm fell into administration in late 2020 after the heavy impact of the pandemic, before being snapped up by current private equity owners Cain International.
This closure plan comes two years after the group previously shut 22 restaurants and cut 216 jobs.
