A total of 1,259 primary care networks became operational today - with just a handful of England's almost 7,000 GP practices expected to be left out at this stage.
NHS England said the launch of PCNs would mean that patients would get 'longer appointments with their family doctor' as the networks allow practices to support each other and bring in new support staff.
PCNs - backed by £1.8bn in funding over five years starting from 2019 - are expected to employ around 20,000 staff to support primary care, including physios, pharmacists and social prescribers.
But RCGP chair Professor Helen Stokes-Lampard warned that there was no guarantee that PCNs would deliver immediate benefits to general practice across England.
Primary care networks
She said: 'PCNs are essentially groups of practices working together and aiming to work with other agencies to deliver improved care for patients - and collaboration can have great benefits, particularly at a time when general practice is facing such intense resource and workforce pressures.
'However, there is no one size fits all approach to resolving the pressures facing general practice, and while structural reorganisation like this can be positive for surgeries with sufficient resources, others will need a lot more support and time to develop.'
The RCGP chair warned that networks must be allowed to develop from the bottom up, rather than being imposed - and that other promises set out in the NHS long-term plan would also have to be delivered to support GPs.
NHS England chief executive Simon Stevens said: 'Strengthening general practice is a central part of the long-term plan, and PCNs have the potential to bring about the biggest improvement for a generation.
'As the PCNs get up and running in the coming weeks and months, patients will begin to see the benefits, freeing up GPs to focus on the sickest. This new way of working allows us to keep all that’s best about British general practice, while future-proofing it for the decade ahead.'