The agency found dioxin emissions for March were nine times over the pollution limit. Research shows they can increase a risk of cancer.

The agency records dioxin pollutants every six months.

But Nottingham's Friends of the Earth want the emissions to be monitored continuously instead.

Emission levels

Spokesman Nigel Lee said: "This a concern not just in terms of the amount of dioxins that it's going to pump out from time to time, but all the other pollutants such as mercury, heavy metals and so on - which they also don't continuously monitor.

"We don't know how much of these sorts of pollutants are actually coming out of the incinerator."

But Mark Haslam from the Environment Agency said the level of pollution was tiny.

Further tests

The incinerator is owned by Waste Recycling Group (WRG).

The company declined to be interviewed, but said in a statement: "WRG is now working with the Environment Agency and consultants to carry out further tests to identify why the breach occurred and to prevent further breaches.

"Even if both lines had breached the emissions limit, which they did not, the levels emitted would have been just 16% of the World Health Organisation's recommended tolerable daily intake of dioxin for the most exposed individuals.

"This is the first breach since dioxin started being monitored at the plant 10 years ago."