Three-quarters of containers inspected last week at a UK port contained illegal waste, an Environment Agency team found.
The week-long intelligence-led inspections were part of a Europe-wide operation to crack down on the growing problem of illegal exports of waste going between, in, and out of European countries.
Environment Agency environmental manager John Burns said: "Some companies appear to be abusing the rules and exporting waste illegally and without the relevant permissions. The transfrontier nature of waste shipments means it is crucial to work together with customs and our European partners to tackle this problem."
No waste can be sent abroad for disposal under current regulations, though certain wastes can be sent abroad for reuse or recycling with the recipient country's approval. In most cases the relevant environmental authorities must also be notified.
Several containers were detained and enforcement action will be taken against those where evidence of illegal activity exists.
Burns said: "When inspected, the suspect containers which were described as having paper for recycling were found to contain mixed rubbish including plastics, textiles and rotting food infested with maggots."
The Environment Agency fear that illegally exported waste can have serious health and environmental implications as it is untracked and unrecorded. The fear is that it will simply be dumped in developing countries.