asked the Secretary of State for the Environment what is the statutory requirement under which commercial metering devices installed by regional water authorities are required to be of approved design and accuracy and subjected to routine inspection by trading standards officers.

None. No regulations have been prescribed under either Section 11 of the Weights and Measures Act 1963 or Section 32 of the Water Act 1973 to require water meters to be subject to such approval and inspection. However, consumers are doubly protected; firstly, by the dispute procedure provided by paragraph 59 of Schedule 3 of the Water Act 1945; secondly, by the offence provisions of section 16 of the Weights and Measures Act 1963.