The Long Covid SOS charity called on the Government to stop putting its "head in the sand" and take action to reduce the growing number of long Covid sufferers.
Patients were asked if they were still experiencing symptoms more than 12 weeks after they first had Covid-19, that could not be explained by something else.
Of the 6,555 respondents in Liverpool, 418 (6.4%) said they had symptoms of long Covid – one of the highest rates in England.
Applying this rate to the latest population estimate for the CCG area as a whole means 26,428 people aged 16 and over in the area could be suffering from lingering health problems.
Across England, 4.4% of GP patients said they had long Covid symptoms – which can include fatigue, shortness of breath, and heart palpitations – around 2 million people.
Long Covid SOS said this rate is higher than estimates by the Office for National Statistics, but it is also possible that many people may not be aware that they have it at all.
Ondine Sherwood, co-founder of the charity, said most sufferers are unable to obtain any meaningful treatment, and for many even that is not available due to lengthy waiting lists.
She added: "The Government needs to acknowledge that this is a major issue impacting a significant proportion of the population and that it will lead to a massive burden of ill health on the NHS, on society and the economy.
"The Government needs to stop putting its head in the sand and start to act."
She said stricter infection control measures, more healthcare investment and increased research funding are needed.
The GP survey showed that the vast majority (83.5%) of patients who responded to the survey in Liverpool said they did not have long Covid symptoms, but 8.9% said they were unsure and 1.3% preferred not to answer.
The Royal College of GPs said post-Covid syndrome is still a relatively new condition, but the prolonged health effects that some experience can have a terrible impact on their lives.
Professor Martin Marshall, chairman of the RCGP, said more resources are needed, including good access to appropriate rehabilitation services in the local community, and more staff working in general practice.
He is calling on the Government to address the "intense workforce shortages" and help deliver care to the increasing number of patients with long Covid.
The Department of Health and Social Care said more than £50 million has gone to help scientists understand the virus's long-term debilitating effects, while the NHS has committed £224 million to support people with ongoing symptoms.
A spokesman added: “The best way to protect yourself from Covid is by getting the vaccine, and our world-leading programme has delivered over 150 million jabs.”