Nine out of 10 GPs who took part in a poll by Londonwide LMCs said that if the draft plans went ahead, the financial stability of their practice, the stability of their workforce and the overall viability of their PCN would be undermined.
Of just over 700 GPs who responded to the survey, carried out to inform the LMC's feedback to an NHS England consultation on the draft plans, 99% said 'resources outlined in the service specifications' were not proportionate to the activity required from practices or networks.
The same proportion of respondents said there were not enough GPs within their PCN or practice to deliver work required of GPs in the plans, or to oversee the work of other staff.
Meanwhile, 99% of GPs responding to the survey also said there were not enough non-medical staff within their practice or PCN to deliver work required through the network DES - and they were not confident that staff could be hired in time.
Londonwide LMCs chief executive Dr Michelle Drage said: 'Our grassroots GP practices have sent a clear message to NHS England and Improvement that however many opportunities the system believes PCNs may offer, it is core general practice that is key to delivering them and it is the core of general practice that must also be sustained.'
One GP responding to the Londonwide poll said: 'The resources provided are completely inadequate for the activity these proposals expect from a PCN. This represents a substantial increase in GP workload - not a decrease as promised. It is clear that the excessively hastily introduction of PCNs has been ill-thought out and is completely undeliverable on the ground.'
Another said GPs 'with substantial experience of work in care homes are clear that the "targets" are unachievable'. He pointed out that care homes where GPs carry out 'ward rounds' currently pay privately for the service, which falls outside core GMS work - and warned that 'if this were no longer funded, the only way to deliver such rounds would be to remove GP clinics, further restricting both appointment availability and choice of doctor'.
Other respondents said there were not enough non-medical staff to carry out work expected of PCNs in the draft specifications - and that GP numbers were too low to supervise extra staff.
The future of the £1.8bn PCN programme - a core element of the five-year GP contract that took effect from April 2019 and of the NHS long-term plan - has been left in serious doubt by the strength of GPs' response to the draft network DES proposals.
Senior GPs in leadership roles within PCNs have quit or threatened to pull out, some LMCs have urged doctors not to sign the contract unless changes are made - and last week the BMA's GP committee voted to hold an emergency conference once contract talks between its executive committee and NHS bosses are complete, after rejecting a package of contract measures on offer for 2020/21 including the DES plans.
After consultation on the draft plans closed last week, NHS England said that 'whatever the views of respondents about the specifications, we view such widespread engagement in a debate about how PCNs develop as a positive change and a learning opportunity'.
NHS England added: 'We want to be absolutely clear that we have heard the views expressed. We will now carefully consider how to respond adequately, balancing the ambition to improve services for patients across England and the need to stabilise general practice, with what can realistically be delivered by PCNs in 2020/21.'
The consultation is understood to be the first time that the GP profession as a whole has been offered the chance to provide feedback on draft GP contract plans.