The company has spent about �1m on its new store in Bala

The firm received a complaint after the alleged comments in front of customers at its store in Bala, Gwynedd, a heartland of the language.

A spokesman said the company took the matter extremely seriously.

But he said it had received conflicting versions of what had actually happened.

Elwyn Edwards, a councillor representing Bala, said he was dismayed to learn of the alleged comments.

If we find that these comments were true then they were certainly highly inappropriate and do not reflect company policy Pete Williams, Somerfield

Mr Edwards said: "I thought this kind of thing was past now.

"Imagine coming to a town like this, where 90% of the people are speaking Welsh, and telling this girl not to speak her own language in her own country. It's not on."

Mr Edwards said the person accused of making the comment was an area manager, and not the store manager, who was local and had the respect of people in the town.

Somerfield operates about 1,250 stores throughout UK town centres and has invested around �1m in the Bala store.

Company spokesman Pete Williams said the company would make sure it found out what happened.

He said: "If we find that these comments were true then they were certainly highly inappropriate and do not reflect company policy.

"We are currently conducting a thorough investigation.

"We have senior HR (human resources) managers who are actually interviewing staff at the store just to discover what the facts are and we will take appropriate action if it's found to be the case."

In a statement, the firm said: "Our divisional executive (area manager) David Ware, who is at the centre of this allegation, has lived and worked in Wales for many years and has immense respect for the local community and for the Welsh language.

"We endeavour to embrace the local communities in which our stores operate and have just invested almost �1m in our Bala store and have no intention of upsetting any of our customers or staff.

"We are determined to get on with the job of operating the Bala store as a successful local fresh food store which reflects the needs of local customers."