Thousands of people could be left struggling for healthcare after the company behind the city's busiest GP surgery announced it is going bust.
One Norwich Practices, which runs the Rouen Road NHS walk-in centre, has confirmed it will be closing in "the coming months" due to financial turmoil.
It has left NHS bosses scrambling to find alternative providers for the services it provides - which also includes the vulnerable adults services and the GP surgery in Rouen House, which has more than 10,000 registered patients.
The decision places uncertainty over how the thousands of people who rely on the company will instead access healthcare should alternative providers not be found.
Tracey Bleakley, chief executive of NHS Norfolk and Waveney, said: "We are naturally disappointed that this decision has had to be made.
"Our priority now is to minimise the level of disruption to patient services and ensure that patients are able to receive the care they need.
"We have been and will continue to work closely with colleagues across the Norwich primary care network and ONP to continue to provide patient services through the transition period, while also securing alternative providers to take on the full suite of services that they were contracted to deliver."
It comes after a lengthy period of uncertainty around the future of the walk-in centre - which NHS bosses had considered closing.
Paul Wood, interim chief executive of ONP, said: "It is with great sadness that we have come to the difficult conclusion that ONP cannot remain financially and operationally sustainable beyond 2023.
"We will be working very closely with NHS Norfolk and Waveney ICB (Integrated Care Board) to ensure an orderly transition and we will assist in the development of service transfer plans to safeguard services and transfer over as many staff as possible to the new provider or providers once these are identified.
"We will not be making any statutory redundancies until we know the outcome of the service transfer plans."
It is hoped new providers will be found to replace the services offered by ONP - which also offers healthcare access for asylum seekers and runs an asthma service in schools.
But councillors fear it would have disastrous effects.
Lucy Galvin, Green city councillor, said: "This shocking news is highly concerning.
"It's potentially a disaster for healthcare in the city as there will be a huge knock-on effect on all other local provision - many services will struggle to fill in the gaps, as will A&E at the hospital.
"Most importantly, patients at staff at all the One Norwich services deserve clarity on what this announcement means for them now and their access to vital healthcare, and for staff, their jobs."
Concerns about the organisation's financial situation were expressed earlier this year when a study into the walk-in centre conducted by Healthwatch found it was running at a loss.
Alex Stewart, chief executive of Healthwatch Norfolk, said: "We are very concerned about the circumstances that led to this announcement.
"Just 12 months ago, One Norwich was forecasting a growth in turnover and income and an ambition to develop new services.
"A lot appears to have changed in that time.
READ MORE: Norfolk and Waveney GP waiting times revealed in new figures
"Communication is key in the weeks ahead and we would urge ONP and NHS Norfolk and Waveney to ensure people are kept informed transparently, accurately and efficiently about the care."
In August alone, 12,731 appointments were held at the Norwich Practices Health Centre in Rouen Road - not including the number of people using the walk-in centre.
The figure makes the practice the busiest GP surgery in the city area - and the second busiest in Norfolk overall.
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