Last weekend I witnessed an incident in a local petrol station. A young man wanted to purchase a can of petrol. The cashier refused to sell it to him as he looked under the age of 16 - the legal limit.

The lad protested for a short time explaining that her colleague had sold to him the day before and that it simply was not fair that he was now being denied. He added that his friend with him actually was 16 and could legally make the purchase. The cashier would not be moved and quietly stuck to her decision that she had to have proof of age before she would make the sale.

The youngster was clearly miffed, so I hung around a bit just in case there was trouble. Thankfully none materialised and the young man set off, presumably to find either a proof of age or a different and more accommodating (and therefore unlawful) petrol station.

This kind of scene plays itself out in many different retail establishments every day. Knives, solvents, alcohol, cigarettes, petrol and fireworks are among the products that shopkeepers are not allowed to sell to people below a certain age, be it 16 or 18.

Steadfast

I was very impressed by the steadfast nature of the cashier as she refused, because research has shown that refusal to sell age-restricted products is the most common cause of verbal abuse towards shop staff, and can even provoke physical violence. As many as 90 per cent of shop workers surveyed have suffered some form of abuse, many on a daily basis. In 2006 alone, retail staff reported more than 63,000 incidents of verbal abuse from customers.

Last year I supported the Freedom From Fear campaign, run by retail workers' union Usdaw to highlight the plight of shopkeepers. It is encouraging that, according to the latest figures, violent attacks and verbal abuse suffered by shop staff have declined. I pay tribute to the campaign run by Usdaw, which has raised awareness of the problem of abuse faced by millions of workers who serve us each and every day in shops.

I believe that one way to address the problem of assaults on shop workers is to foster a culture of "no ID, no sale". This means that customers will know that if they look under 21 years of age to a shopkeeper then they must show proof of age before purchases. This would help to diffuse tension and reduce the opportunities for confrontation when a customer is challenged about their age.

Proof

This is why I have co-sponsored a Bill introduced in Parliament last week. The Bill proposes to introduce a nationally-recognised proof of age scheme. At the moment there are approximately four nationally recognised proof of age cards and 20 local authorities have entitlement cards which provide proof of age. These local cards are not accepted in all parts of the country as proof of age and are therefore of little value outside the immediate vicinity of that local authority area.

Therefore, a single national scheme would, I believe, simplify the position on proof of age both by removing the myriad of schemes and by raising the profile of such a scheme in the minds of customers and retailers. A more entrenched "no ID, no sale" culture might take some of the pressure off shopkeepers, providing fewer opportunities for confrontation and therefore less abuse and fewer assaults on shop staff.

I would very much like to hear your views on these proposals. You can get in touch with me by post at Lyn Brown MP, House of Commons, London, SW1A 0AA, by e-mail on lyn@lynbrown.org.uk or by telephoning my office on (020) 7219 6999.