Officers have been visiting residents to give advice on what people should be putting in particular bins as the authority looks to cut costs in the face of increasing budget pressures.
The council said that recycling being put in the wrong bins ends up being rejected at the plant and leads to increased costs to taxpayers.
So far in this financial year, Walsall Council has forked out more than £200,000 on transport and disposal charges as well as other costs to take the contaminated recycling to landfill or incinerators.
Other figures show the contamination rates have risen from an average of 11.7 per cent in 2016 to the current rate of 14.58 per cent.
Clean and Green officers said, alongside some plastics, clothes, shows, used disposable nappies and food waste continue to cause problems.
Councillor Oliver Butler, portfolio holder for clean and green said: “The reality of the situation is that if residents contaminate their recycling bins this costs them money.
“It costs around £45,000 per year for every one per cent of recycling that is contaminated.
“This means that there is less money available to spend on the things that residents tell me are important to them, such as picking litter, sweeping the streets, cutting the grass, spaying the weeds, and tackling fly tipping by opening the tips seven days a week.
“Putting the wrong things in the green recycling bins means that huge amounts of local council tax payers’ valuable money is literally going to waste.
“One of the myths I often hear is that recycling is washed at the recycling centre. This is not the case, there is no giant dishwasher.
“Secondly people need to understand that this waste has to be sifted by the human hand first. Would you like to stand at a conveyor belt having to pick through soiled nappies and waste food?
“I can certainly assure residents that the stench is far from pleasant.
“If you have a larger household you may be entitled to bigger grey bin and both of our tips (HWRC), which are free to use for Walsall residents are open seven days a week with late night opening twice a week.
“So there really is no excuse for residents contaminating their bins and not recycling correctly.
“Supporting residents at the very start of the recycling process, to put the right items in the right bins, will help to raise the quality of the loads we send to our recycling contractor so that they aren’t rejected and sent for incineration.
“With the best will in the world, we can’t recycle used nappies or the remains of last night’s takeaway curry – these items need to go in the grey bins.”