The Department for Transport has published guidance for passengers and industry on the GOV.UK website on the use of plastic bags to carry liquids through UK airport security. This includes advice on the nature of the plastic bag required. Many UK airports also provide guidance on their websites.
The Civil Aviation Authority provides advice and guidance for airports on the definition of a liquid. The main regulation covering liquids, aerosols and gels, EU Regulation 185/2010 also sets out the rules and requirements.