The owner of Frankie & Benny's and Chiquito chains is to sell or close 33 restaurant sites.
Around 500 jobs will be at risk as a result of the closures, but the firm said it would try to relocate employees in its other outlets.
The Restaurant Group, which also owns Joe's Kitchen and Garfunkel's, said its restaurants had failed thanks to "insufficient focus on value" and "unsuccessful menu development".
It has not been revealed which restaurants will be shut, but the firm said it will close 14 Frankie and Benny's venues and 11 Chiquitos immediately.
Company chair Debbie Hewitt added: "In 2015, we began to introduce more 'authentic' menus without sufficient testing of the concept.
"This led to the removal of many popular dishes from the menus and led to a further decline in covers.
"We are now clear about where we want to focus, who we want to measure ourselves against and how we will deliver.
"We have a detailed action plan, with many actions already underway."