65.—(1) A supplier must not, in respect of energy supplied under a supply contract, unreasonably—
(a)increase the rates at which it charges any amounts payable by the customer under the supply contract,
(b)expose a customer to any additional risk, or
(c)change any of the following so they are less favourable to the customer—
(i)the terms of the supply contract;
(ii)the terms on which the supplier offers to enter into supply contracts;
(iii)the process by which prices or charges payable under supply contracts are set;
(iv)the way in which the supplier exercises its rights under its supply contracts.
(2) For the purposes of determining whether a supplier has behaved unreasonably in doing any of the things referred to in paragraph (1)(a) to (c)—
(a)a supplier’s conduct is, in particular, unreasonable if, and to the extent that, the conduct, or the supplier’s ability to retain the customer as a customer while engaging in it, is facilitated by the existence or operation of the scheme;
(b)it is, in particular, reasonable for a supplier to increase its charges—
(i)to its customers collectively, by an amount that in aggregate does not exceed the efficiently incurred costs of complying with these Regulations;
(ii)to any customer, by an amount that does not exceed its fair and reasonable share of such efficiently incurred costs.