London GPs take Save Our Surgeries campaign to Downing Street
Campaigners fighting new funding arrangements for GPs' surgeries are delivering a 21,000-signature petition to Downing Street.
The group, Save Our Surgeries, says 22 practices in Newham, Tower Hamlets and Hackney could be forced to close, if proposed changes go ahead.
They are calling on NHS England to reverse funding cuts.
NHS England said it recognised "the unique financial challenges some GP practices were facing".
The government has decided to phase out the Minimum Practice Income Guarantee (MPIG) nationally, over a seven-year period and changes started taking place in April.
The MPIG was introduced in 2004, to support some GP surgeries and was used to top-up the core funding of practices.
Campaigners say practices in inner-city deprived areas will be worst hit.
Dr Naomi Beer, GP at Jubilee Street Practice in Tower Hamlets, east London, one of the affected surgeries, said: "Our patients often tell us how much they appreciate the high quality, accessible service that Jubilee Street provides.
"We've already taken pay cuts to try to keep going, but we can't absorb such a huge loss."
An NHS England spokesman said: "The decision to phase out Minimum Practice Income Guarantee (MPIG) is national policy which is being implemented all across the country, in order to make GP funding more equitable.
"The majority of practices in London will gain as a result, however we recognise the unique financial challenges that some GP practices are facing as a result of these changes.
"That is why we are working with the affected practices, the Office of London CCGs and Local Medical Committees from across the capital, to consider how these changes can take effect, and what arrangements might be put in place to support those affected."