Local government chiefs are calling for labelling on packaging to be made clearer, to avoid recyclable waste getting mixed-up with non-recyclable items.
Department for Environment, Food and Rural Affairs data shows 6,271 tonnes of waste collected by Northumberland County Council were rejected at the sorting point in the year to March – up from the 5,257 tonnes the previous year.
Recycling charity Wrap estimates that waste disposed of as recyclable – then found not to be – costs councils around £93 per tonne to dispose of.
That means rejected waste in the area cost an estimated £583,203 in 2020-21.
David Renard, environment spokesman for the Local Government Association, blamed manufacturers who produce non-recyclable plastic packaging, which people put in the recycling bin “in good faith”.
He said: “The burden then falls on councils to not only collect it and dispose of it, but to pay the extra cost of disposing of it.
“At a time when councils are working towards achieving net zero, they are doing so with one hand tied behind their back, courtesy of manufacturers who are littering our communities with plastic they know cannot be disposed of sustainably.”
A Defra spokeswoman said: “We want to make recycling easier and consistent. Our landmark Environment Act will transform the way we deal with rubbish."
The act will see all food and garden waste collected separately from dry recycling and residual waste.