An environmental campaign group is taking legal action against the government over proposals that it claims could fast-track chemical hazard classifications from other countries with lower standards into UK law.

Fighting Dirty claims proposals to change the classification and labelling of potentially hazardous chemicals could result in the UK weakening standards on cancer-causing substances.

Last year, the Health and Safety Executive (HSE), which since Brexit has been responsible for the regulation of chemicals in Britain, launched a consultation on plans to change the system, which determines the substances that are identified as hazardous, the warnings that appear on labels, what restrictions apply and whether chemicals are banned or tightly controlled.

Its consultation proposed that the HSE should be allowed to fast-track chemical hazard classifications from other countries into British law. When the HSE published its response to the consultation findings, it said it would recognise the EU’s standards when adopting such hazard classifications. The EU has the highest standards on chemical safety globally.

But when the government laid the regulations before parliament earlier this year, the EU and its standards were not mentioned. Fighting Dirty is taking legal action against the government over concerns that this omission may expose the public to more hazardous chemicals.

Ricardo Gama, a partner at the law firm Leigh Day, which is representing Fighting Dirty in the proceedings, said the absence of this “safeguard” meant the government, or any future government, “could approve chemicals from places that have lower standards than the UK and EU”.

Fighting Dirty has said substances classified as human carcinogens by the International Agency for Research on Cancer, such as hexavalent chromium – the highly toxic chemical made infamous through the film Erin Brockovich and the water pollution scandal – are far more widely used in countries such as the US, China, India and Brazil than in the EU.

The campaign group argues the new regulations would give the HSE “unchecked power” to import weaker standards for chemicals such as this into British law.

“This is deregulation dressed up as efficiency, and the British public will pay for it with their health,” said Georgia Elliott-Smith, the founder of Fighting Dirty.

The HSE says the legislation will help to prevent non-EU jurisdictions with weaker regulatory practices from qualifying for fast-track evaluations, but campaigners argue the omission of the EU in the text means future governments could still approve chemicals from places that have lower standards than the EU.

Chloe Topping, a senior campaigner at the charity CHEM Trust, said the omission “risks the regulations being misused in the future”.

Elliott-Smith said: “We are not asking for anything radical. We are asking the court to hold the government to its own promises and ensure laws designed to protect people from cancer-causing chemicals actually do their job. If this law goes unchallenged, it could shape how chemicals are regulated in the UK for generations to come.

“We want our government to take the science far more seriously, and to be far more cautious and apply the precautionary principle here to protect the health of its citizens over the profit of corporates.”

Topping has also urged the government to “close this door by clarifying in the legal text that they only intend to use the changes to speed up adoption of decisions made by the EU, which sets the highest standards globally on chemical safety”.

A spokesperson for the HSE said: “Far from opening the door to lower standards, these regulations actually provide for a mechanism by which Great Britain can prevent non-EU jurisdictions with weaker regulatory practices from qualifying for fast-track evaluation – helping protect the public and the environment.”

A formal letter before the claim was sent to the HSE on 1 April. Fighting Dirty is now proceeding with an application for a judicial review.