The law governing electrical safety in England and Wales is the Electricity at Work Regulations 1989. The law is enforced by the Health and Safety Executive.
To avoid prosecution the installer must be able to demonstrate ‘due diligence’ by showing that the Wiring Regulations BS7671 have been followed.
The IEE wiring regulations (called BS7671 "Requirements for electrical installations") is a comprehensive document giving minimum acceptable standards and practical guidance on the installation and maintenance of electrical services.
The possession of a C&G 2382 Certificate is demanded by most employers.