The company behind restaurants such as Wagamama and Frankie & Benny's has said that 10% of its sites will not reopen before the end of the year.
The Restaurant Group said that the sites, largely in airports, will open next year at the earliest, as they are unlikely to attract enough customers to make reopening worthwhile.
The affected sites are in areas "where footfall is anticipated to remain considerably week (primarily in some airport locations)", the company said in an update for shareholders on Friday.
It raises concerns for the jobs of those who work at the sites, as the Government's furlough scheme, which covers salaries, will end in October.
All the stores that will reopen this year will have started serving customers by the end of September, the company said.
Meanwhile, 60% of its sites that open sometime before the end of August will be given a chance to take advantage of the Government's new Eat Out to Help Out scheme, which gives diners up to 50% off their meal during the first three days of the week.
One in four of the Restaurant Group's restaurants and pubs will be open by the end of this month.
"The group has now started a phased reopening of its restaurants and pubs for eat-in trade in line with Government guidance," it told investors.
"We are very pleased to be able to welcome back our customers and colleagues ensuring that their safety is paramount, whilst maintaining an enjoyable experience.
"The diversified portfolio of the group allows each division to adapt to the challenges of social distancing uniquely, whilst keeping the customer at the heart of every decision."
The news comes at a turbulent time for the company.
Last month it announced that 125 Frankie & Benny's sites will close permanently, with 3,000 jobs on the line.
It will be left with around 400 restaurants and pubs after the restructuring.
The company's board took a 40% pay cut at the start of April as they tapped into Government furlough money.
They have now upped their pay, but will still take 20% less than normal until all staff are off Government-backed furlough.
The announcement comes a day after the Burger King UK CEO warned that up to 1,600 jobs could go with the permanent closure of 10% of sites.
Last week it emerged that almost 2,000 jobs will be lost after Casual Dining Group, the owner Bella Italia, Cafe Rouge and Las Iguanas, called in the administrators, saying it would close 91 of its 250 restaurants.
Meanwhile Upper Crust and Ritazza owner SSP, known for serving transport hubs around the UK and overseas, announced plans to shed up to around 5,000 jobs - almost half its workforce - as a result of plunging passengers numbers at train stations and airports due to the coronavirus pandemic.
