Scottish Power is warning that a proposed Welsh language law could cost energy companies millions of pounds and lead to hikes in bills for customers.

Scottish Power owns the Manweb electricity supply business in North Wales. It is not presently required to provide a service in Welsh, however it already operates a bilingual service for customers in Wales.

Some 6,000 customer calls each year are in Welsh compared to a total of 7.2m a year across its customer base in Great Britain.

But the Welsh Assembly wants to introduce new legislation that would involve a statutory demand for companies to increase Welsh language services.

Scottish Power said: “To give some sort of scale, we believe that a significant extension of Welsh language provision by our energy retail business could have a set-up cost of around £1.5m, plus ongoing costs of over £500,000 each year. These costs would inevitably need to be reflected in tariffs.”

The company explained that SP Manweb offers all customers in Wales the option of using Welsh or English.

“While this proportion [less than 0.1%] is very small and gives some indication of the proportionality of any undue spending in this area, we believe that offering our customers the opportunity to speak in Welsh is important.”