The first wave of new polyclinics will result in the closure of more than 100 GP surgeries in London alone, it has been reported.
Some patients have already received letters informing them of proposed relocation into the new supercentres, according to Pulse, the newspaper for GPs.
Plans have been drawn up to shut sites run by eight primary care trusts - including Haringey, Ealing, Kensington and Chelsea, and Camden, although NHS London said it could not confirm exactly how many practices would be relocated.
London is set to be followed by Birmingham, Liverpool and Yorkshire and the Humber, all of which are developing their own plans for polyclinics.
"The government keeps insisting surgeries will not be forced to close to make way for polyclinics, but the reality is closures are already in motion," said Richard Hoey, deputy editor of Pulse.
"Polyclinics will have some advantages, certainly, but the benefits of flash new buildings and access to specialist services come at a cost, in terms of travelling time and continuity of care. The pros and cons need to be properly debated, and it's incredible that changes are coming at such a breakneck pace."