Dr Dixon, who lost out this year to Dr Terry Kemple in the race to become the next RCGP president, said he had assumed when the NHS Alliance began that everyone shared his impatience to improve patient and community care and health.
'I had assumed these attitudes were rife throughout the health service but have found that too many people are more concerned about protecting their own interests and the status quo,' he said. 'I believe that NHS Alliance is one of the few true champions of the NHS.'
Dr Dixon said the NHS was now being transformed at 'unprecedented pace and scale', and that the NHS Alliance had achieved its primary goal - 'to see healthcare shaped by the clinicians delivering it at the frontline'.
His decision to step down comes as the NHS Alliance moves to reposition itself to fit a more integrated health service model.
'The time for single-focus organisations representing discrete parts of the system has gone,' Dr Dixon said. 'It’s not about "hospitals" or "primary care" anymore, nor about siloed membership or representation.
'Our vision for the next phase of NHS Alliance is as a virtual organisation with light-touch governance but firm direction, harnessing digital and social media, and based on crowd-sourcing principles of "followship" rather than restrictive membership.'
Dr Dixon - a GP at the College Surgery in Cullompton since 1984 - was an early advocate of clinical commissioning, advocating and setting up GP-led commissioning schemes from the early 1990s.
He was an advisor to Labour health minister Lord Ara Darzi on practice-based commissioning and is currently on an NHS national strategy group for clinical commissioning.