Ministers have refused to disclose details about their discussions with local authorities and the food industry over possible disruptions to food supplies in a no-deal Brexit, arguing the information could damage negotiations with the EU.

The Green MP Caroline Lucas, who unsuccessfully sought the information in parliament and then via a freedom of information (FOI) request, said it was “reckless and irresponsible” for ministers to use this argument to withhold potentially vital facts from the public.

The ruling, in which the Department for Environment, Food and Rural Affairs (Defra) argued there was “a strong public interest” in keeping the information secret, follows the release of documents outlining the government’s planning assumptions for its no-deal Brexit preparation plan, called Operation Yellowhammer.

The documents, published after MPs passed a Commons motion on Monday calling for their release, said freight delays could mean supplies of “certain types of fresh food” would be reduced, with some prices rising, which could particularly affect vulnerable groups.

The FOI request from Lucas sought access to Defra’s discussions about food supplies and prices in the event of a no-deal Brexit, with food industry bodies as well as local resilience forums, which group together councils, emergency services, the NHS and others to plan responses to localised disorder and emergencies.

It also asked for more general information about planning assumptions over food supplies and prices if no deal happened, as well as representations made by food industry groups and organisation such as charities and food banks.

In its response, Defra confirmed it held the information, but said it would not release it on public interest grounds, arguing: “At this stage in our negotiations with the EU it is of vital importance that the government only release information, and at the appropriate time, when it is unlikely to impact those negotiations,” the reply said.

Lucas said the public had “every right to know what ministers know about disruption to food supplies and prices in the event of a no-deal Brexit”.

She said: “Yet this government is shamefully withholding this basic information, whilst their attempted reassurances directly contradict what the food industry itself is saying.

“We are being kept in the dark about the availability of food in less than two months’ time so Boris Johnson can continue his sham negotiations with Brussels. It is hard to think of anything more reckless and irresponsible: Boris Johnson’s play-acting over a Brexit deal is being put ahead of people’s right to know what food might be available for them, their families and their communities.”

Kate Dalmeny, who heads Sustain, a food and farming campaign that has worked with charities and others over the possible impact of no deal, said: “We are increasingly worried that a no-deal Brexit would be disastrous for millions of people on low incomes, who would struggle with predicted food price rises of up to 10%, with no means to stockpile food.”

A Defra spokeswoman said: “We already have a highly resilient food supply chain, and a food industry that is well versed in dealing with scenarios that can impact food supply. Half of the food we eat is produced right here in the UK and consumers will continue to have access to a wide range of high-quality food.

“We are meeting regularly with the industry to make sure they are fully prepared for leaving the EU on 31 October,” she added.