The poster displayed in London features a caption saying that in parts of north Wales, people believe cow saliva helps hair grow back.

Mark Tami MP: 'Protect Wales' image'

But Alyn and Deeside MP Mark Tami has written to the pharmaceutical firm behind the ad for Regaine, claiming it insults people.

The hair product ad was designed to be harmless fun, but Mr Tami singled out the caption referring to north Wales as a cause of concern.

"On a superficial front the advert is harmless and lighthearted," he said.

'Jibes'

"However, the Welsh are being singled out, possibly as an easy target.

"I doubt Regaine would risk displaying this advert over the border," said Mr Tami.

"I have written to the company - some might say we should laugh at such jibes but at some point you have to take a stand and protect the image of your country," he added.

Anne Robinson: Upset Welsh MPs

Weakest Link presenter Anne Robinson was accused of insulting north Walians, after comments she made on the Paul Merton show Room 101.

MPs called for her alleged "racist" comments to be investigated.

Ms Robinson later apologised for any offence caused and she appeared in a promotional advert for the Wales Tourist Board.

But BBC director general Greg Dyke was questioned last month by detectives from Wales about Ms Robinson's comments.