Electricity bill dispute with the landlord

Before the period of tenancy there was some defect in electricity meter and it was showing undereading resulting into less bill .We stayed in the flat for 11 months(paid the bills on time) and were never told by the landlord about the defect of electricity meter during the period of tenancy. The landlord is now charged by the electricity department for the difference in reading and landlord have rectified the meter and now after 8 months of leaving the flat he is asking to pay the difference amount during the period of tenancy.Please advice and refer the relevant act and clause on the issue