The campaigning chef - who returns on Monday with a new show Return To School Dinners - criticised the parents for delivering fish and chips, pies and burgers to children at Rawmarsh Comprehensive in Rotherham every day.
Mums Julie Critchlow, aged 43, whose 15-year-old daughter and son, 11, attend the school, and Sam Walker, whose 11-year-old son is a pupil there, organise the junk food run daily.
But a spokesman for Jamie, aged 31, who is currently in Australia, said: "If these mums want to effectively shorten the lives of their kids, then that's down to them.
"What people don't realise is that junk food doesn't just make our children fat, it's also a growing cause of malnourishment.
"Many kids just aren't getting the nutrition they need to grow healthy."
The Star revealed yesterday how the mums take orders from the kids at breaktime and then buy the food and deliver it to the pupils in an old supermarket trolley at lunchtime.
They have been criticised by the school's headteacher John Lambert and healthy eating campaigners.
But the mums say the pupils do not like the food on offer at the school and claim they are not being given enough choice.