Campaigners have called on MSPs to take action, complaining that sexually-explicit material has now become commonplace.

But Justice Secretary Kenny MacAskill will today argue that obscene material is already controlled by law, and that a voluntary code of practice is in place for material that is not illegal.

He will argue the Scottish Government case at Holyrood's Public Petitions Committee, which has been considering the issue for more than a year.

Margaret Forbes, on behalf of Scottish Women against Pornography, petitioned the MSPs in June 2008 with a plea for the Government to ensure magazines and newspapers with sexually-graphic covers were not displayed at children's eye-level or next to youngsters' comics.

She told the committee: "Children see this material from a very young age when they are taken shopping with their mothers.

"Boys grow up believing that this is what girls and women are all about, desperate with sexual encounters with every female they meet, and girls grow up thinking that this is what they should aspire to."

She told of seeing a magazine on sale at a supermarket with an "offensive" photograph on the front - clearly visible even though it was six feet off the ground.

She said: "Pornography is now so common it is like wallpaper in our lives."

But the Scottish Government argues there are already "substantial" legal and voluntary controls on the sale of sexually explicit material.

A spokesman said: "We would be concerned if there was an indication that materials being displayed were illegal and, if that were the case, the matter would be reported to the police for investigation,

"In contrast the material that is referred to in the petition, while it may be offensive to many, is legal to display.

"Despite that, the industry, through the National Federation of Retail Newsagents, has taken a responsible attitude by introducing a voluntary code of practice which urges its members to be sensitive to the concerns of consumers and makes recommendations as to the positioning of these magazines and newspapers in retail outlets."