Campaigners have urged health secretary Jeremy Hunt to pull the plug on the service, warning that patients joining the service have destabilised other GP services.
Hammersmith and Fulham CCG has warned that it needs a bailout of around £18m in 2018/19 to cope with the surge in patients arriving at the Lillie Road Medical Centre, which hosts the GP at Hand service.
The patient list registered at the practice has increased from 4,970 in November 2017 to 29,588 at the start of June 2018.
Of the 24,618 patients who have joined in that time, almost 21,000 are aged between 20 and 39 years old - confirming GP leaders' concerns that the service would disproportionately attract younger, healthier patients.
Patients who register with GP at Hand are required to quit their existing practice and sign up as out-of-area patients with the Lillie Road practice.
The service restricts registrations from patients likely to have complex needs, such as pregnant women or those with some long-term conditions, leading to accusations of cherry-picking. Patients who sign up can receive video consultations remotely, or face-to-face consultations if needed at locations around London.
GP at Hand and Babylon, the company whose technology it relies on, have said repeatedly that 'patients and GPs are flocking to GP at Hand because they recognise the potential that high quality, digital-first 24/7 NHS GP services bring'.