Between the week ending December 28 and January 4 there was a 42 per cent rise in children of that age taken into hospital with coronavirus in the south east of England.
This was an increase of 50 to 71 patients in that time.
One health watchdog leader said it was ‘extremely concerned’ by the data.
Roger Batterbury, the chairman of Healthwatch Portsmouth, said: ‘Healthwatch Portsmouth are carefully watching the data on all the hospitalisations locally and are extremely concerned at the number of children, especially those under six needing to be in hospital.
‘We are acutely aware that hospitals are calling major incidents as a number of staff are off with Covid and demand is currently outstretching capacity. This, in itself is of grave concern, and we are monitoring the situation and asking questions of the trusts.’
It comes as the Joint Committee on Vaccination and Immunisation (JCVI) has only recommended Covid vaccines for children aged 12 and above.
Current advice is that children aged between five and 11 should only be vaccinated if they are clinical risk group or live with someone who is immunosuppressed, while vaccines are not offered to those aged below five.
Mr Batterbury added: ‘Healthwatch Portsmouth has always followed the advice from public health and taken note of the science. We wait to see if the JCVI research data recommends Covid-19 vaccinations for younger children, at which point we would support the NHS campaign to encourage eligible younger children to be vaccinated.’
Portsmouth South MP Stephen Morgan, urged government to ‘get a move on’ with vaccinating children.
‘It’s really concerning to see a significant rise in Covid hospital admissions amongst young children in the south east, particularly as this has been avoided in previous waves,’ he said.
‘Ministers must redouble their efforts to drive down community transmission with vaccines and testing, and support local hospitals which are also dealing with significant staff absences.
‘The government missed an important opportunity to get all children aged 12 to 15 vaccinated over the Christmas break, and must now get a move on with vaccinating primary age children. This, plus ensuring an even supply of tests will help children and parents stay as safe as possible.’
However, Helen Atkinson, the director of public health in Portsmouth, attempted to downplay the concern.
She added: ‘We are not aware of an increase within our local hospitals but it's important we keep a close watch on the data and that our residents follow public health recommended measures to reduce the virus spreading such as washing hands regularly, wearing a face covering, keeping 2m apart and letting fresh air in.’
The region with the highest increase in hospital admissions for children under six was the north east and Yorkshire, which saw an 80 per cent rise in that week.