NHS England is to transfer its Primary Care Support Services to private firm, Capita in September, prompting speculation that 29 sites could close with the loss of 800 jobs.
The contract to run the care support centres is reportedly worth between £400m and £1bn for up to 10 years.
The staff provide administration services for NHS primary care providers including GPs, opticians, pharmacists and dentists.
An NHS England spokesman said, “These proposals would release substantial administrative savings to reinvest in frontline health services and will form the basis of full consultation with the employees involved.'