Morrisons supermarket group has apologised after it labelled a chicken product as containing British poultry and “non-EU salt and pepper”.

The decision to detail the origin of the ingredients on its £4 oven-ready chicken crown prompted a threat of boycott from some customers.

The company, which has long prided itself on the sale of British produce including “100% British fresh meat, milk and eggs”, immediately backtracked, telling customers the non-EU part of the label was a mistake.

“The wording on the packaging is an error for which we apologise. We are changing the packaging immediately,” it tweeted.

It is understood that the labelling was a result of a “misinterpretation of packing and labelling regulations”.

After Brexit, label rules largely follow EU regulations – which state any food product marked British by flags or words must include a statement about the origin of any “primary” ingredients that are not British. In Morrisons’ case the name of the product included salt and pepper, so they are classed as “primary” elements and their provenance must be stated on the label in 75% of the size of the font used for the word “British”.

The incident is the latest sign of a new front in the culture wars opening on supermarket shelves with some who agree with packaging that celebrates Britishness and others who do not.

On Tuesday Morrisons said it was fully compliant with labelling rules but did not want to get drawn into Brexit culture wars.

“Our chicken label is adhering to British packaging regulations, however we will be redesigning it to make it clear this is not a political commentary,” it said.

One customer, David Bright, said: “I’m done with shopping @Morrisons … I can live with union flags on bananas, but the gratuitous slight on the EU is too much.”

Another customer tweeted: “Have I missed this new trend for our groceries to celebrate their exclusion of any EU condiments?”

Ghislaine Hull wondered why Morrisons made a point of advertising the fact the condiments it was using were both non-British and non-EU.

“Aside from anything else I’d have thought most normal people want to know where foodstuff IS from not where it isn’t.”

Others liked the label because it was divisive. “Have to say a very well done to Morrisons, this has upset all the right people.”

The controversy comes as supermarkets navigate the meaning of post-Brexit Britain in labelling.

A Crosse & Blackwell survey this year revealed more than half of British shoppers are looking to buy more domestic food.

But some are put off by what they see as a politicisation of food, objecting to labels celebrating Britishness.

One customer described the union flag on Mornflake porridge oats as “very unpleasant and quite intimidating”.

And last summer Co-op supermarket was mocked in some quarters after it labelled a package of ice cubes as “made with British water”. “What next, British air?” quipped one customer on social media.

“Brexit may be behind us now, but make no mistake: a divided country remains,” Callum Saunders, head of planning at Zeal Creative, which works with Nestlé, Pringles and McCain, told The Grocer earlier this year.