In section 143 of that Act (charges schemes) after subsection (3) (charges which may be imposed in certain cases) there shall be inserted—

“(3A)

A sewerage undertaker is under a duty to ensure that any charges scheme made by the undertaker, so far as having effect to recover the undertaker’s costs of providing a sewer by virtue of its duty under section 101A(1) above, causes those costs to be borne by the undertaker’s customers generally; and a sewerage undertaker’s duty under this subsection shall be enforceable under section 18 above—

(a)

by the Secretary of State; or

(b)

with the consent of or in accordance with a general authorisation given by the Secretary of State, by the Director.”