A giant Bradford chemical company has been ordered to improve its procedures after three-and-a-half tonnes of highly flammable solvent overflowed from a cooling vessel.

Ciba Speciality Chemicals has been warned it must establish robust management systems for monitoring staff following an investigation by the Environment Agency. It has been issued with an Improvement Notice and told that, if it fails to comply, the agency could consider further enforcement action which could result in prosecution.

Today the firm apologised for the incident and pledged it had instituted an action plan to prevent a repeat of the incident at its Low Moor plant.

The material released during the incident on July 24 - dearomatised solvent - is classified under Control of Major Accident Hazards regulations because of its flammable nature. The agency's investigations concluded that bad operating practices led to the release.

Agency regulatory officer Chris Gaughan said: "No one was put at risk as a result of this incident, but there is no room for complacency when dealing with potentially hazardous substances.

"The company was found not to be taking all necessary measures to prevent major accidents and to limit their consequences to people and the environment."

Rodney Swails, site director for Ciba, said the company had held "good meetings" with the Environment Agency and Health and Safety Executive to discuss the incident.

He said it was caused by an "operating problem" and admitted "the people involved got it wrong".

He said: "We are very sorry about it, but the HSE and Environment Agency have agreed that our action plan is the best way forward."