The government has quietly changed its guidance on the number of days within which people with coronavirus symptoms should get tested, the Guardian has learned, raising fears that the disease could spread quicker. On the government’s website, people are now told: “On day eight, you need to go to a test site” after an apparent change on Friday morning. Earlier in the day it was quoted as saying: “You need to get the test done in the first five days of having symptoms.” Various internal messages seen by the Guardian show coronavirus helpline team leaders suggesting the tests do not provide an accurate result more than five days after first having symptoms. “If over five days, the tests will not provide an accurate result,” one said. Staff reacted with surprise and bemusement to the change, made without announcement or explanation. The reason behind the move was unclear, but there will be suggestions that it is intended to help manage stretched capacity. To control the spread of coronavirus, it is vital that potential carriers are identified as swiftly as possible after exhibiting symptoms, and experts said the change made the spread of the virus more likely. Prof Allyson Pollock, a member of the Independent Sage committee, said extending the time period in which symptomatic people can be tested could lead to infectious people not being identified soon enough, further undermining the effectiveness of contact tracing. “The priority for the government should be to find symptomatic people early and to follow the statutory notification system, which requires medical practitioners to notify suspected cases to local authorities,” she said. “This can only be done by integrating testing into clinical care in primary care settings and through local contact tracing. “The problem is, the government has carved testing out of health services and general practice and public health and created a centralised, ineffective, privatised testing and contact-tracing system instead of rebuilding public health and primary care and NHS lab capacity locally.” She added that the extension also risked the tests identifying more people who were no longer infectious and could result in the unnecessary isolation of contacts. The test used in the UK is not a test of infectiousness, experts have said, as it does not distinguish between those who have the virus and are infectious and those who are no longer infectious. There have been many false results as a consequence. John Ashton, a former regional public health director and author of the book Blinded by Corona, said testing after eight days was as useful as a “chocolate fireguard”. “The horses will have bolted, with more people becoming infected,” he said. “This is out of the same playbook as downgrading the classification of the virus severity to justify less PPE. Once you are symptomatic, you are infectious. It’s a disgrace.” Prof Ian Donald, from Liverpool University, tweeted: “This new govt policy will increase the likelihood of infection.” The NHS has updated its website following the move by the government, but a number of clinical commissioning groups, including Leicester City and Kent and Medway, still advise people to get tested within five days. This also remains the NHS Scotland advice. The Department of Health and Social Care (DHSC) refused to comment. It is understood that the new eight-day cutoff reflects what the government considers the latest clinical and public health advice on the most appropriate window for testing. This advice is said to be under constant review, but the DHSC did not share any new evidence with the Guardian. The government’s largely privatised testing regime has been roundly criticised after many people with suspected coronavirus were unable to get tested and others were asked to travel hundreds of miles. Serious problems remain across the country, with many people still unable to access tests easily. Labour’s Tanmanjeet Singh Dhesi raised this with the health secretary, Matt Hancock, in the House of Commons on Friday, and was told there was record testing capacity. “I will not have this divisive language, I just won’t have it,” Hancock said.