Defra has left the British potato industry scratching its head after revealing that just 17% of the potatoes the department buys come from the UK.

The surprisingly low figure was disclosed by food and farming minister Jim Paice in a written statement to the House of Commons earlier in the week.

By contrast, 100% of the beef and 90% of the poultry bought by the department was British, Paice said. He also stated that, excluding potatoes, 96% of “indigenous, in-season” fruit and veg bought by Defra came from the UK.

The figures given by Paice refer to the period between September and December 2011.

The low proportion of British potatoes initially prompted suggestions that Defra must have got its figures wrong, especially as home-grown potatoes account for more than 70% of domestic consumption. Defra confirmed that the 17% figure was indeed correct, however, but would not comment further on why so few of its potatoes were British. A spokeswoman said the government was not able to insist its caterers use only British produce “because it would be illegal under EU trade rules”.

It is also understood the 17% figure refers to prepared potato products as well as fresh potatoes. But NFU food chain adviser Lorna Hegenbarth said the figure was very low, even if a lot of prepared products were included.

“It does depend on the mix of potato products bought – if it’s a lot of chips and fried products, then historically caterers have generally chosen Dutch  products, citing quality and supply issues around British products,” she said. “But there are some strong British brands now that operate in the public sector, so if they want to, caterers can choose products other than Dutch.”

She added: “If the purchasing mix has larger volumes of peeled potato and jacket potatoes, then 17% is pretty poor.”

Defra’s catering contractor, Eurest, which is part of the Compass Group, said it could not comment on the Defra contract specifically but stressed it fully supported the UK potato industry and all its “seasonal fresh potatoes” were British.

“We follow the potato season from Cornwall to Scotland, buying more than £1m worth of potatoes from UK farmers every year,” a spokeswoman said. “Wherever possible we buy seasonal British fruit and vegetables, and within our Defra contract 96% of the remaining in-season fruit and vegetables supplied are sourced in the UK.”

Despite only 17% of potatoes coming from the UK, Defra appears to be making progress in ramping up the proportion of British-produced food in other areas. Paice’s statement revealed that 57% of all meat bought by Defra between September and December came from the UK, compared with 43.5% between May and September. The department is also buying more British poultry – 90% of the poultry it bought between September and December was British, up from 67.1% between May and September. He did not give figures for potatoes for the period between May and September.

Overall, 61% by value of the food bought by Defra between September and December came from the UK. Defra introduced a new department-wide catering contract in May 2011, which means its current track record on buying British cannot be compared with earlier years on a like-for-like basis.