Dutch shops and supermarkets are currently paying an average of 10% more for one in 25 products because they cannot buy from wholesalers in other European countries, according to research carried out on behalf of the economic affairs ministry.

A litre of cola, for example, can cost €1.50 in a Dutch supermarket but €1.07 in a German chain, broadcaster NOS said. Chocolate spread, shampoo and ketchup are also among the products which can be cheaper to buy in Germany.

The researchers found half of the 44 big buyers in the Netherlands are facing so-called “territorial supply constraints (TSCs) and are being told to buy the goods at the Dutch branch of the supplier or are refused the goods outright.

Around 300 businesses said they face the same problem, research bureau Ecorys found. All main seven supermarkets, including market leaders Jumbo and Albert Heijn reported they could not buy in A brands beyond the Dutch borders.

Caretaker economic affairs minister Micky Adriaansens has said there is no place for buying restrictions for shops and supermarkets in the EU internal market and will petition for a European ban. She commissioned the research following complaints by the retail sector.

“This can lead to higher prices for consumers, a lower profit margin for retailers and a more limited range of products,” the minister said in a reaction.

Adriaansens said the investigation confirms the existence of TSCs and that she would ask for a European ban on the practice, starting with a legal ban in the Benelux countries.

A complicating factor for buyers is that products sold in the Netherlands must have labels in Dutch. Online supermarket Picnic dodged that European rule by buying cheaper products in Germany and putting Dutch labels on them, a practice the researchers said is “expensive and logistically complicated”.

The solution to that problem could be to provide digital labelling via QR codes but this puts people who don’t have smartphones or have no digital skills at a disadvantage.

The researchers said that the ban would not immediately lead to cheaper products at the supermarkets but that prices would drop in the longer term as a result of more competitive buying.