An Irn Bru advert has been condemned as "sickening and disgusting" because of its sexual overtones.
Irn Bru has been criticised in the past for its adverts
But Barrs, the company which makes the soft drink, says it has no plans to remove the billboard posters.
The advert shows a young girl wearing a bikini beside the slogan "I never knew four-and-a-half inches could give so much pleasure".
The Scottish National Party's Sandra White said she was disgusted by the poster, claiming the connotations were in very bad taste.
She added: "I am not amused by this advert, but am disgusted by it.
"Before, I have laughed at many Irn Bru adverts but the connotations of this one are in very bad taste.
"They're trying to sell their products with sexual connotations and they don't need to go down that road.
"In this day and age you want young kids to have confidence in themselves so I'm quite disgusted that Irn Bru have sexed up their adverts.
"Young people like Irn Bru because of the taste, not because of sexy connotations.
"I think they're going down the wrong road and it is in very bad taste."
The organisation Family and Youth Concern is warning that the promotion could put customers off Scotland's so-called "other national drink".
Spokeswoman Ann Boyle said the advert, created by the Leith Agency, was ill-advised and distasteful.
"They're not the only company to use sex to sell a product. But this is a national drink and it appeals to people of every age."
A spokesman for Barrs defended the advert, saying that four-and-a-half inches is the size of a can of diet Irn Bru and that the company cannot be held responsible for "other people's interpretations".
A spokeswoman for the Advertising Standards Agency (ASA) said it had not received any official complaint about the advert.
But Irn Bru ads are not strangers to controversy.
A row was sparked after a poster poked fun at Goths, with the slogan: "Cheer up Goth. Have an Irn Bru."
Followers of the fashion trend claimed they were bullied and had cans of the drink thrown at them after the ad was launched.
Earlier this year angry TV viewers condemned a commercial in which an unborn baby was seen drinking a can of Irn Bru in the womb.