European commission gives legal guidance to member states to take action on sale of lower-quality goods in eastern Europe.

Brussels has published legal guidance and offered funding to help governments crack down on food and drink multinationals’ illegal selling of inferior versions of well-known brands in eastern Europe.

Věra Jourová, the most senior justice official at the European commission, said evidence showed the practice broke EU law and she wanted member states to have the confidence to act against the perpetrators.

Companies accused by EU countries of selling lower-quality goods bearing identical branding in the east to the west include Coca-Cola, Pepsi, HiPP baby food, Birds Eye, Lidl and Spar. Persil and Ariel have also been accused of selling a less effective formula in eastern Europe.

The companies deny any suggestion they have misled consumers. They claim the ingredients of their products are different only because of consumer preferences.

But Jourová said she was pleased to learn that HiPP was among the brands relaunching products in response to an outcry, as revealed by the Guardian this week.

The commissioner said she would not yet name and shame those who she believed had broken the law, but was willing to encourage consumers to boycott certain products if companies persisted with illegal practices.

“Presenting two different products in the same branded packaging is misleading and unfair to consumers,” she said.

“This issue is a clear example that we can solve cross-border problems only when working together on EU level. For too long, member states alone couldn’t find the right way to address this. I am determined to put an end to this practice, prohibited under EU law, and make sure that all consumers are treated equally.”

The guidance given to member states on Tuesday provides them with the legal argument to prosecute companies that fail under EU food information regulation to give truthful and sufficient information about a particular product.

They are also being helped to enforce the unfair commercial practices directive, which prohibits, among other actions, marketing identically branded products in a way that has the potential to mislead consumers.

The commission has made €1m (£880,000) available to its Joint Research Centre to develop a methodology to allow cross-border tests and comparisons, and €1m to member states for the financing of studies or enforcement actions.

However, the move was attacked by Fred Roeder, the managing director of the Consumer Choice Center, an organisation campaigning for deregulation, who said the commission was responding to populist voices in eastern European governments.

“No one forces consumers to purchase any particular brand. They are free to pivot to other products if they aren’t happy with the taste or consistency of some offered brands in their country,” he said.

“Given that this doesn’t happen much, it shows that food producers apparently hit the local median taste with their regionalised strategy of ingredients. Calling for mandatory harmonisation of the taste of products all across the EU neglect the reality of a diverse union.

“Stigmatising different tastes and consistency of food products to an east-west conflict is mere populism. There are also massive differences in taste, consistency, and colour among fairly homogenous groups of countries. This is driven by consumer preferences and choice.”