Aldi and Pets At Home will be opening two new stores in Buckingham after planning permission was granted by Aylesbury Vale District Council last Thursday.
The branches will take over the former Focus store on the A421 Buckingham bypass, creating two unite and up to 35 jobs.
But the plans have not been welcomed by town centre businesses, including Buckingham Pet Foods which will directly compete with the new shops.
Ali Hurst, who runs the Market Hill business with her partner Paul Thomas, said it was disappointing the application had been approved.
She said: “Buckingham itself will suffer, it is known as a market town and they want everybody to shop in the town but they are moving everything out of town with lots of free parking.”
Elliot Wallis, chairman of Shop Buckingham, said people had changed the way they shopped over the last 20 years and were not going to high streets to do their weekly shopping.
He added: “The town centre has been there for years and if people are not using it now, they never will. It will start to drag people out of town but it might start to bring people in to the town so it evens itself out.”
Asda first applied for permission to convert the former Focus store more than a year ago, an application which was broadly welcomed in Buckingham. Planning permission was granted and some time after that Asda sold the Osier Way site to Aldi.