A second coronavirus wave could be twice as big as the first because the NHS Test and Trace system is not good enough to stop it, experts have warned.
Currently, the system is said to be reaching only around 50% of contacts but a spike will hit in December without improvement.
Schools opening in September could fuel the crisis, scientist Professor Chris Bonell warned.
He said the NHS Test and Trace system "is not good enough basically".
The expert went on: "We're suggesting schools have to go back in September. It's so critically important for the economy but also for children's educational wellbeing.
"Our study should not be used to keep schools shut over a fear of a second wave but as a call to action to improve the infection control measures and test and trace."
This damning verdict on the government's flawed testing system came in a paper from the London School of Hygiene and Tropical Medicine, where Professor Bonell works, and University College London.
The Mirror reports modelling found NHS Test and Trace, which is staffed largely by outsourcing firms such as Serco, needs to reach more than two-thirds of contacts to avoid a second deadly Covid-19 wave.
This latest study found in a worst-case scenario the wave could be 2.3 bigger than the first.
If things don't improve, this means we could be heading for a second national lockdown.
But just one in seven people with virus symptoms are coming forward to get tested and be entered on to the contact-tracing system.
Shadow Health Secretary Jon Ashworth said: "Boris Johnson promised us a world-beating test and trace system.
"Instead the system isn't tracing enough people."
Professor Bonell said public confidence may have been hit by Dominic Cummings breaching lockdown rules when he drove from London to Durham with signs of coronavirus.
He went on: "This really requires that the population has trust in the system which may not always be the case at the moment in the aftermath of Dominic Cummings.
"A key factor that has to be considered is the proportion of those who are told to isolate, are actually isolating."
NHS Test and Trace has no data on how many of those contacted follow rules as it doesn't carry out follow-up calls.
Modellers estimate 70% of staff will return to their workplaces once schools are reopened, solving childcare problems.
