The cost is based on GPs and nurses working flexibly for no extra pay.
Mr Johnson visited Churchill Medical Centre in Kingston, Surrey, which has opened from 8am to 8pm four days a week, and 9am to 11am on Saturdays for nine months, to hear about its extended hours experience.
Dr Peter Smith said: 'We are now looking to implement the service in an inner-city practice in Derby to show that it can be done elsewhere.'
Mr Johnson refused to comment on his visit.
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