Environmental campaigners have launched a last-ditch legal bid to prevent or delay the UK’s trade deal with Australia, owing to concerns over its impacts on the climate and the natural world. A group of seven environmental and farming organisations has filed a formal complaint alleging that the UK government breached international law in signing the deal, which they fear is about to pass into law without any further in-depth parliamentary scrutiny. Opposition is also building within the House of Lords, with several peers telling the Guardian of their reservations that the trade deal could pass while the government is under a caretaker prime minister and parliament in the grips of the Conservative leadership contest. The green groups – including WWF, Sustain, Green Alliance, Compassion in World Farming, the Soil Association, the Trade Justice Movement and the Tenant Farmers’ Association – have taken the legal action under the Aarhus convention, an international agreement that requires public consultation on decisions by the government or public sector that have an impact on the environment. Their complaint could also have an impact on future trade deals, as the government could be told it must include more input from the UK public in future deals. Under the Australian trade deal, the UK could be opened up to Australian beef and other farm products that are subject to lower standards, including on the use of antibiotics on livestock and of harmful pesticides, than are legal in the UK. Research for green groups also shows that the trade deal could have a severe effect on deforestation in Australia, by encouraging more land to be turned to ranching and to grain production for herds. Several peers told the Guardian they were worried the deal was being rushed through. Lady McIntosh of Pickering, the Tory peer who as Anne McIntosh MP chaired the influential environmental, food and rural affairs select committee in parliament, said: “This is the UK’s first new post-Brexit trade deal, and the process by which it is passing through parliament is inadequate. The government has not brought forward a trade strategy, the trade and agriculture commission can only advise after it has been signed, and the parliamentary scrutiny arrangements have been very weak. “UK farmers face rising energy costs, higher fuel prices and an acute shortage of labour, especially of seasonal farm workers, which means many of them are going to struggle. We may well face a social crisis in our rural communities if we do not look after the uplands and our hill farmers. This deal is clearly an asymmetrical agreement as it is more advantageous to the Australian farmers than our own. “MPs should have an opportunity to question ministers and scrutinise this trade agreement before it is signed to ask what the benefits of this deal will be to the UK. But it appears this will get waved through with no debate.” Lady Rosie Boycott, the cross-bench peer who served as “food tsar” for London under Boris Johnson when he was mayor, added: “Australia has an abysmal record on deforestation, animal welfare and climate. The government’s own advisers conceded that overuse of pesticides in Australia would give their farmers a competitive advantage over the UK’s. Australia uses many more highly hazardous pesticides than the UK, many of which are banned here on health and environmental grounds. How will UK consumers be protected?” She pointed to a petition in 2020 signed by more than 2 million people calling for food standards to be protected in trade deals. The deal was struck under the previous Australian government, which took a strongly climate-sceptic view and often dismissed environmental concerns. Lord Oates, the Liberal Democrat peer and former chief of staff to Nick Clegg, said the government should look to rewrite the deal now that Australia had a new government committed to strong action on the climate crisis. He said: “It is deeply disappointing that our government is refusing to take advantage of the election of a new Australian government to strengthen the extremely weak climate provisions of the UK-Australia free trade agreement. As Cop26 president, we are abdicating our leadership responsibilities on climate if we do not take every opportunity to strengthen this deal and set a strong precedent for future negotiations.” The legal action under the Aarhus convention is regarded as a last-ditch attempt to force the government to reconsider. However, with the outcome of the Tory leadership contest still in the balance, candidates have spent little time considering the trade deal. Campaigners hope it could be delayed until a new leader is in place. Katie White, executive director of advocacy at WWF, said: “People don’t want the food on their plates to fuel the climate and nature crises. Yet behind closed doors the UK government has cut trade deals with Australia, an environmental laggard, opening our shores to imports without adequate safeguards for climate and nature. “It’s totally unacceptable that the public and parliament have been denied a say on these trade agreements when their consequences will be felt for generations to come – full scrutiny is essential if we are to avoid a deal by default.” Kath Dalmeny, the chief executive of Sustain, a coalition of food and farming groups, said: “The government has failed to set a trade policy, failed to consult the public and failed to give parliament enough time to consider the UK-Australia trade deal. “Involving parliament and the public in the trade deal scrutiny process should be seen as a strength, not a weakness. Multiple sets of advisers and select committees have told the government they should set core food, environment and animal welfare standards for imports, which we would urge them to do as quickly as possible.” A DIT spokesperson said: “We carry out considerable consultation on new trade deals and have always been clear this deal will not compromise our high standards. The independent Trade & Agriculture Commission’s report agrees that the UK-Australia agreement does not undermine the UK’s environmental protections – and in some cases strengthens them. “Our deal with Australia will unlock £10.4bn of bilateral trade, while also securing substantive provisions on climate change and reaffirming our commitment to the goals in the Paris agreement – the first time Australia has included these in a trade agreement.”