Policing underage sales is putting retailers in an impossible situation, says shopworkers' union USDAW.

Speaking after the publication of its survey on retail abuse, which found that 82% of shopworkers have been subjected to abuse as a result of asking for ID, general secretary John Hannett said that retailers were "damned if they asked, and damned if they didn't".

"Age-restricted sales are a minefield for our members to negotiate," he said. "If they make a mistake and sell alcohol to a customer under 18 they risk being prosecuted and receiving a fine. On the other hand, asking for age identification often leads to abuse from frustrated and angry customers."

Usdaw wants the government to launch a consumer awareness campaign about age-restricted sales, and introduce a single voluntary national ID card to make verifying age easier.

"We'd also like to see a change in the law to make it an offence for an underage person to attempt to buy any age-restricted product, not just alcohol, or for an adult to proxy purchase," Hannett added.