Radical cost-cutting changes to the healthcare system could see call centres set up to handle GP appointments, a review has suggested.
The move has been recommended in a document commissioned by the Department of Health, which sets out a series of possibilities for saving £600m a year through the streamlining of "back office" functions in the NHS and "sharing" services.
Its authors said GPs should "review the possibility" of moving to national or regional call centres for appointment-based bookings.
They added that the cash saved could be "redirected" to support frontline services.
The document, published by the Foundation Trust Network, proposed that back office services should be configured at scale on a national, regional or multi-regional basis for commissioning organisations (PCTs and GP commissioners) from April 2013.
It said: "A specific area of work which offers significant potential for increasing efficiency is the back office functions directly supporting the delivery of primary care services.
"The majority of GP practices have dedicated administrative support teams, often undertaking identical tasks, including the organisation and booking of patient appointments.
"This system should be radically re-engineered."
The document added: "There are substantial efficiency gains to be achieved through transforming GP back-office functions, such as the potential to move towards regional and national GP appointment centres."
A spokeswoman for Unison said: "The fact is that (GP practice) staff not only make appointments, they are dealing with patients, sorting out patient records, ensuring appointments are made with hospitals and getting results back.
"A call centre cannot begin to do the job that these staff currently are expected to do.
"Healthcare is also a very personal service where people need support. They have the right to expect somebody to be there for them."
A spokeswoman for the Department of Health said there were no plans at the department to introduce call centres.