Diana Johnson, Labour MP for Hull North, is backing a campaign to help shopworkers when serving age-restricted products.
Usdaw, the retail union, has highlighted this issue as being a major cause of violence, threats and abuse against shopworkers.
Diana Johnson MP said: "I am very concerned to hear that many shopworkers are being threatened and abused when they ask for proof of age or refuse to serve those they believe to be under-age. In some cases this leads to violence against the shopworker.
"I have just attended an Usdaw meeting where they invited me to guess the age of some youngsters. I have to say I found it very difficult and I have great sympathy with shopworkers who have to do this every working day.
"We need to take the guessing out of age-related sales. I back Usdaw's key campaign aim of a national, robust and single age identification card. This must also be accompanied by a culture of 'No ID No Sale'. Youngsters have to understand that if they can't prove their age then they can't buy the goods. This is also another illustration of the more general case for a workable national ID card scheme."
John Hannett, Usdaw's General Secretary said, "We are delighted to have the support of Diana Johnson MP. This is a very important issue for our members working in retail.
"Shopworkers have a difficult job to do, policing the sale of age-restricted products. If they get it wrong there can be serious consequences. Selling to an under-age person can attract an £80 fine for the shopworker, not the company. Refusing an over-aged person can lead to violence, threats and abuse towards the shopworker.
"A proper age identity card and a culture of 'No ID No sale' will help to take the guessing out of age-related sales."