Inspectors have started checking Dunedin's recycling bins to ensure the proper waste is being put in them.
Contamination of materials destined for recycling has been an issue in New Zealand and overseas.
In Dunedin, the city council says the contamination rate has almost doubled over the past six years from 5.7 per cent to 11 per cent.
It says its inspections, to run for 12 weeks, are aimed at helping people improve their recycling, such as leaving out items like plastic bags and needles.
Council solid waste manager Catherine Irvine says recycling bins could be removed in persistent cases.
She says most residents are keen to recycle and mostly do a good job.
"There are a few common mistakes people make with their recycling, and this is an opportunity to give them some guidance," she said.
"It's only a small minority of people who put general waste or hazardous materials in their recycling bins."