Parents have been urged to “control” their teenagers outside school to stop the spread of coronavirus.

Deputy chief medical officer Dr Jenny Harries said that the risk of transmission in the classroom is “probably much lower” than when teenagers are left to their own accord.

She said schools provide a “controlled” environment, and that the outbreak of coronavirus in Leicester was not down to the return of pupils to classrooms.

Speaking at the daily Downing Street press conference, Dr Harries said: “The original guidance recognised that the transmission risks were potentially more in the social behaviours of the teenagers – the older children out of school – than they potentially were in school.

“School is quite a controlled environment and perhaps trying to encourage families as well – I know it is difficult because I’ve been there – but to try and control their teenagers in their social interactions outside of school as well.”

She added: “In many ways we should be more concerned with what the teenagers are doing outside school. So if they are in school, in a controlled environment, with hierarchies of control and people keeping an eye on them if you like, that’s probably a much lower risk than if they were out of school doing their own thing.”

Education Secretary Gavin Williamson said the school attended by his two teenage daughters had more control over them than he has “ever been able to achieve”.

He also said the rise in cases in Leicester was “not something about schools returning”.

However, Public Health England (PHE) said earlier this week that the proportion of people aged under 19 testing positive for the virus in the city had risen from 5% in mid-May to a current level of around 15%.

Health Secretary Matt Hancock said that even though children are less likely to get ill from the disease, the decision to shut Leicester’s schools was made to try to halt further transmissions.