The government is planning to water down the regulatory requirements on key chemicals, in what experts fear could be the first move to a weaker post-Brexit safety regime for potentially toxic substances. Proposals published last week without fanfare on a government website set out some of the intended new rules for the new post-Brexit national chemicals regulator. The proposals would change the way “substances of very high concern” – which include potential toxins and carcinogens, and chemicals that persist for a long time in the environment – are dealt with. Under EU law, these chemicals are formally identified and publicly listed on a “candidate list”, while authorities analyse them and decide whether to ban them or allow their use in certain circumstances, by transferring them to an “authorisation list”. Companies must inform regulators and their supply chains when dealing with products containing these candidate list chemicals, encouraging them to use alternatives. Under the government’s proposals, companies will not be obliged to submit information on “substances of very high concern”, but will be allowed to do so on a voluntary basis. Only chemicals likely to be transferred to the “authorisation list” would be listed on the “candidate list”, meaning a smaller number of notifiable chemicals will be analysed. Zoe Avison, policy analyst at the Green Alliance thinktank, said: “Relying on voluntary data submissions by chemical companies will almost certainly see hazardous substances falling through the cracks. The UK could have made sensible arrangements to reduce costs for industry and safeguard public health. Yet the government has boxed itself into a corner. After the new delay for companies to submit safety data for the UK market, this is a very worrying sign for the future of chemical regulation in the UK.” Experts told the Guardian they were concerned the government’s move would weaken protections against harmful substances, and allow potentially toxic chemicals to slip through the net. Michael Warhurst, executive director of Chem Trust, a charity that campaigns on harmful chemicals, said: “It seems that the government is putting in unnecessary layers of information requirements before taking action, which will lead to regulatory inaction on a range of harmful substances. This will open the door to British consumers and the environment having greater exposure to harmful chemicals than in the EU, and second-rate system for regulating chemicals post-Brexit.” Jamie Page, of the Cancer Prevention and Education Society, added: “We are concerned that protections that British citizens previously enjoyed are now being eroded. The more the UK diverges from the EU Reach [registration, evaluation, authorisation and restriction of chemicals] system and database, the more likely people are to be exposed to potentially hazardous chemicals.” The proposals by the government will not be subject to public consultation and will not require a vote in parliament. Under post-Brexit legal arrangements, ministers can make such alterations without discussion. A spokesperson for the Department for Environment, Food and Rural Affairs said: “We are committed to maintaining an effective regulatory system for the management and control of chemicals, which safeguards human health and the environment and can respond to emerging risks. We have published our interim approach to the candidate list in UK Reach. This approach aims to ensure we have a single, coherent approach to nominating substances for the candidate list.”