A High Court judgment last week reopened the debate about product 'use-by' dates, to the dismay of some campaigners

A landmark legal case revolving around a batch of frozen pigs' tongues could change the way food use-by dates are enforced in the country.

High Court judges ruled earlier last week that a business accused of selling food past its use-by date could counter a prosecution under food labelling laws by showing the product had in fact not needed a use-by date. Consumer experts fear that this interpretation could allow retailers to sell out-of-date food. The matter is being viewed as a test case for use-by dates, and similar cases across the country are being put on hold while it is dealt with.

"All consumers should have this case on their radar because this could determine whether or not standards are weakened that currently protect public health," said Tim Lang, professor of food policy at City University in London. He added there was still unnecessarily high food poisoning and one of the means by which consumers had been protected was through the "messy system" of sell-by dates and so on. He said the system did need "sorting out" but, in the process, there should not be a weakening of hygiene.

In September, Gwent magistrates cleared a food processing business, Douglas Willis, of 31 charges brought under food labelling laws by trading standard officers at Torfaen County Borough Council, after they found meat products – including pigs' tongues – past their use-by dates in freezers. The company's lawyers successfully argued there was no case to answer because the food was frozen and therefore was not highly perishable and did not need a use-by date.

The magistrates said the council failed to prove a necessary factor required under European law: that the food was highly perishable and, in consequence, likely after a short period to constitute an immediate danger to human health. However, the local authority challenged the decision and High Court judges last week ruled that "the Justices erred in their approach in law" and ordered that the case should be reheard by a different panel. However, they stressed that neither the prosecution nor the respondent had won the appeal.

In their ruling, Lord Justice Aikens and Mr Justice Maddison said, in order to obtain a conviction under food labelling laws for selling food past its use-by date, prosecutors have to prove that – at the point of delivery to the consumer or a caterer – the food is highly perishable and needs a use-by date. However, if a product which requires a use-by date is then frozen, the need for a date still stands. The burden would be on the defendant to demonstrate a use-by label had not been required. If caught by trading standards officers, a retailer selling out-of-date food could attempt to prove that the food was not highly perishable and so did not need a use-by date.

Torfaen's lawyers have applied to the High Court for a certificate stating that the issues raised in the case are ones of general public importance. If granted, it is likely the council will petition the Supreme Court for permission to appeal.

The legal wrangle comes at a time when a wider debate is raging over use-by dates. They cause supermarkets and consumers to throw away huge amounts of food every year. According to Wrap, the government-funded waste reduction adviser, households throw away 7.2 million tons of food each year. More than half of that is £12bn worth of food that could have been eaten.

A spokesman for the Food Standards Agency said the department was "still considering the full implications of the judgment".

Date lines: What supermarket packaging labels mean

Use by Relates to food safety and appears on products that go off quickly. The Food Standards Agency advises there should be no flexibility with a use-by date and that it can be dangerous to eat foods beyond this date.

Best before Relates to food quality and appears on products with a longer shelf life. Using food after the best-before date does not mean it is unsafe, but the quality – such as taste – may not be as good. It is not against the law to sell food past its best-before date. Either a use-by or best-before date is required under European law.

Sell by This has nothing to do with labelling regulations, as the marking is usually put on by retailers to help staff with stock rotation.

Display until Like the sell-by date, this is for supermarket staff. Consumers should ignore sell-by and display-until dates.