LONDON (Reuters) - England risks losing control of the coronavirus pandemic again because it is starting to lift its lockdown without a fully operational track and trace programme in place, three senior scientific advisers warned on Saturday.

Prime Minister Boris Johnson has said England’s lockdown measures will be eased cautiously from Monday, aided by a track and trace system that launched on Thursday.

The advisers warned, however, that the system was not yet in full operation and risked being overwhelmed by the around 8,000 new infections that are still occurring every day outside of hospitals and care homes.

John Edmunds, from the London School of Hygiene & Tropical Medicine and a member of Britain’s Scientific Advisory Group for Emergencies (SAGE), said the government was taking a risk.

“Track and trace was only launched the day before yesterday, so we can’t be sure that that is working effectively yet and yet we’re going ahead and making these changes anyway,” he told Sky News. “I think that that is rather dangerous.”

Edmunds’ comments were echoed by two other SAGE members: Peter Horby, also the chairman of the New and Emerging Respiratory Virus Threats Advisory Group (NERVTAG), and Jeremy Farrar, the director of the Wellcome Trust.

One of the slowest countries to lock down, Britain is now one of the worst-hit by the pandemic, with more than 48,000 deaths and more than 270,000 people testing positive.

To try to contain the virus while also allowing the economy to recover, the test and trace system will ask contacts of people who test positive to self-isolate for 14 days, even if they have no symptoms. An app is not yet ready for the scheme.

Horby of the University of Oxford said there was still too much uncertainty about what would happen to the virus’ reproduction rate — commonly known as R — if schools reopen and other activities resume.

He added that the track, trace and isolate system was not expected to be fully operational - with local teams working to stamp out clusters of cases - until the end of June.

“Returning to a situation where we’ve lost control again is far worse than a week or two of social measures,” he told BBC Radio.

Government officials have repeatedly said they are following “the science” as they respond to the pandemic, but Edmunds said the decision to ease the lockdown from Monday was political.

“My frustration has been recently at least that they’re pretending that they’re not making a decision, that in fact it’s us who are making the decision, and that’s not really the case,” he said. “They have to make the decision and clearly they have.”

The prime minister’s office said it had at all times been informed by the data and evidence. “This package of measures has been carefully designed so we can ease the burdens of lockdown while expecting to keep R below one.”

The devolved governments in Scotland, Wales and Northern Ireland are responsible for their own public health policy.