Mondelez International, which has plants in Chirk and Leominster, said it is stocking up in preparation for a no-deal scenario.
Hubert Weber, the European boss of Mondelez, said the UK was “not self-sufficient in terms of food ingredients” and confirmed the stockpiling as part of contingency plans for a hard Brexit.
The Chirk factory employs about 350 people making chocolate crumb, while Marlbrook near Leominster has 150 staff working on milk products. Both are sent to Birmingham to be made into chocolate bars.
It marks the latest revelation over stockpiling ahead of Brexit as fears mount that the UK may fail to agree terms of its withdrawal by the Brexit deadline next March.
Mr Weber said: “Like the whole of the food and drink industry in the UK, we would prefer a good deal that allows the free flow of products, as that would have less of an impact to the UK consumer.
“However, we are also preparing for a hard Brexit and, from a buffering perspective for Mondelez, we are stocking higher levels of ingredients and finished products, although you can only do so much because of the shelf life of our products.
“We have a contingency plan in place to manage (a hard Brexit), as the UK is not self-sufficient in terms of food ingredients, so that could be a challenge.”
He warned that shoppers may face higher prices and fewer choices if a deal is not agreed and added he wished Britain was “at a different stage (in negotiations with the EU) at this stage”.
Europe is Mondelez’s biggest global division, accounting for 40 per cent of revenue last year.
A raft of firms across the industry are said to be stockpiling and making no-deal plans.
The food and drink industry is one of a number of sectors that are building up stockpiles of raw materials and manufactured goods.
Withdrawal from the European Union will cause delays at borders to carry out customs checks, which are not currently required as the UK is part of the customs union and single market.
Matt Hancock, Britain’s new Health and Social Care Secretary, said in July that officials were considering working with industry to stockpile drugs, medical devices and supplies in the event of a no-deal scenario.
Drugs giant AstraZeneca said in August that patients in the European Union may not be able to receive medicines from the UK post-Brexit if it does not “prepare well” for a no-deal scenario.