The government has defended its test and trace programme in England amid plans to cut 6,000 contact tracers.
Health minister Edward Argar insisted it was a “successful system” and would be strengthened by giving more powers to local public health teams.
The plans mean people who have been in contact with confirmed coronavirus cases may get a knock on their door if tracers cannot reach them on the phone.
Labour said the system was nowhere near “world-beating”.
The shift towards local public health teams follows criticism that the national system is not tapping into local knowledge.
Paul Hunter, professor of medicine at the University of East Anglia, said experts had warned that the system would only work well if it was “done close to the population”.
He said the UK had “many years of very successful, very effective infectious disease surveillance” for diseases like tuberculosis and meningitis – but this skill and experience had not been used.
“I think it was very clear this was not going to be as effective as it could have been,” he told Radio 4’s Today programme.
Asked if money being given to private companies to run NHS Test and Trace needed to be diverted to local councils, Prof Hunter said: “Absolutely. The local councils are already – in terms of the investigation of local outbreaks – showing a very effective system. It has to be run locally.”
When this same suggestion was put to Mr Argar, he said: “We’ve made clear that we believe we still need that national resource, so we’re reducing the size of that contract from 18,000 to 12,000, but we still think that is a vital part of our test and trace system, but we have already given billions of pounds nationally to local councils to support them in their response.”
Serco, one of the outsourcing firms who have been awarded multi-million pound test and trace contracts, last week defended its record – despite figures suggesting that only around 50% of people from the same household as a person infected with Covid-19 were being contacted.
Mr Agar dismissed suggestions that the system did not live up to Boris Johnson’s pledge of being “world-beating” by 1 June.
“We’ve always said that this system would evolve, and what it’s doing here is exactly that: evolving and flexing.”
He said the new plan would use the “scalability” of a national system as well as the expertise and local knowledge of local public health officials.
As part of NHS Test and Trace, public health teams dealing with outbreaks in factories or care homes have consistently reached more than 90% of the contacts on their lists.
Outside of those very localised outbreaks, it is call centres who trace contacts.
But they do not reach as many contacts – their success rate for reaching contacts who don’t live together peaked at just over 70% in the middle of July, but has fallen since then.