The environment secretary has refused to give a firm guarantee that the government will not allow chlorine-washed chicken to be imported into the UK as part of a trade deal with the US.

While stressing that chlorinated chicken was currently illegal in the UK, and that the government was committed to maintaining high standards, George Eustice’s declaration that the government had “no plans” to change the law was more equivocal than assurances given by his predecessor, who said the current law would stay.

In an interview with Sky News’s Sophy Ridge on Sunday, Eustice also signalled that ministers might expand a scheme allowing farmers to hire low-paid foreign workers to harvest crops for 2021.

Theresa Villiers, who Eustice replaced in the recent cabinet reshuffle, said in January that chlorinated chicken and hormone-treated beef were both illegal under EU law adopted by the UK and that “legal barriers to their import” were going to stay in place.

Should you eat chlorinated chicken after Brexit?

When Eustice was asked whether the UK would be willing to relax its rules on these products if that were the price for getting a trade deal with the US, he repeated Villiers’ point about how both were currently illegal. But he also played down the idea that chlorinated chicken would become a key issue in the talks.

“I’m not quite sure why the US would make such demands, because actually chlorine washes on chicken are a very outdated technology and it is not really used by the US any more anyway,” he said.

Eustice said that in the US farmers now used lactic acid washes instead of chlorine washes – a point unlikely to reassure campaigners who object to chlorination not because of the chlorine, but because the process allows farmers to compensate for chicken being kept in unsanitary conditions while alive.

In the interview Eustice said the government was committed to high standards for food safety and for animal welfare. But he refused to give an absolute assurance that the current rules would remain.

“We’ve got a clear position in this country that it is illegal to sell chlorine-washed chicken, illegal to sell beef treated with hormones. We’ve no plans to change those things,” he said.

In a separate interview, Eustice said in the UK lactic acid washes were used for beef but not for poultry, and that there was “room for a sensible discussion” with the US on this matter.

In response, Luke Pollard, the shadow environment secretary, said if the government was really committed to maintaining high animal welfare standards, it should accept a Labour amendment to the agriculture bill banning food imports produced to lower welfare and environment standards.

Pollard said: “Chlorinated chicken being sold in Britain is a genuine risk, unless this backdoor to lower standard US goods imports is closed and a ban is put into law.”

In response to the controversy generated by Eustice’s comments, his department issued a statement saying: “The government will stand firm in trade negotiations to ensure our future trade deals live up to the values of farmers and consumers across the UK.”

Eustice also acknowledged that farmers needed an opt-out from the tight post-Brexit immigration rules recently announced by the Home Office and to hint that the seasonal agricultural workers scheme would be expanded.

Under the plans announced by the home secretary, Priti Patel, from January 2021 it should no longer generally be possible for workers to come to the UK to take up low-paid, low-skilled jobs.

The Home Office said that this year 10,000 people would be allowed entry to the UK to take up seasonal agricultural work, but the National Farmers’ Union (NFU) said that 70,000 seasonal workers were needed to pick fruit and vegetables on British farms.

Eustice said the seasonal agricultural workers scheme was still a pilot and that the 10,000 workers being admitted under it this year was a fourfold increase on the 2,500 allowed when it was launched in 2019.

When it was put to him that the NFU said 70,000 seasonal workers were needed, he claimed that there would not be a problem this year because EU free movement rules still applied during the post-Brexit transition. But in future the 10,000 limit could be increased again, he suggested.

“The important thing will be in the future, and obviously the pilot will end this year, and we will be in a position to roll out a fully fledged seasonal agricultural workers scheme that can be designed to provide the needs of the agricultural and horticultural sector,” he said.