Authors of a report naming Leeds Castle as one of the country’s biggest firework polluters have been branded “killjoys”.

The survey ranks the famous Kent landmark, near Maidstone, seventh on a list of ten major bonfire season displays for increases in the airborne pollutants created.

It was commissioned by a betting firm using data from the air quality monitoring organisation IQAIR.

This year’s Leeds Castle event on November 9 and 10 is a sell-out.

County councillor for the area, Gary Cooke, criticised the report which he says does not take into account the joy and financial benefits to the community.

Cllr Cooke, deputy cabinet member for children’s services at Kent County Council, said: “This sounds like the work of killjoys. Of course, no one wants to unnecessarily pollute the environment but by the same token this is an event that happens for two nights once a year.

“Let’s not forget the enormous amount of family fun and joy it brings to thousands of people and the financial benefit it brings to the local community and a significant local employer.”

The air quality index (AQI) reading was derived from data and showed there was a 109% increase in pollutants immediately after the castle’s fireworks displays.

The highest percentage increase was seen in Manchester at 176% and the lowest (30%) in Birmingham.

Leeds Castle's AQI reading of 119 was the lowest of the ten mentioned in the survey.

The report was commissioned by JeffBet and researchers assessed the country’s top ten fireworks displays over bonfire season.

JeffBet says that “when fireworks explode, they release fine dust particles which contain toxic metals, and smoke from bonfires contains carbon monoxide and pollutant gases”.

A statement from the gambling company said: “In seventh is the Leeds Castle event in Kent. With a grand fireworks display and low light pollution drawing in big crowds every year, the event offers music, projections, and lasers to complement the show.

“The air pollution levels rose 109% overnight in the area, from 57 to 119, a score marked as ‘unhealthy for sensitive groups’.”

“Event organisers should use this data to plan future fireworks displays in large, open areas with a high capacity for attendees, to allow more people to view the same fireworks and prevent the need for multiple events and sessions.

“The air pollution levels will decrease steadily after Bonfire Night, but if you are particularly sensitive to respiratory symptoms, check the air pollution levels in your area, limit outdoor exercise, close all windows, use an air purifier and wear a mask when going out to limit any health impacts.

“If you are suffering with respiratory symptoms, seek medical advice.”

Leeds Castle has been approached for a comment.