The UK government may be undermining its commitments to end deforestation overseas because of conflicts over trade policy, the Guardian has learned. A war of words is raging within the government over deforestation and trade, with green campaigners warning that a proposed policy could have dire consequences for efforts to stop illegal logging. Anne-Marie Trevelyan, the international trade secretary, is believed to want to relax tariffs for goods including palm oil from Malaysia, a country of top concern over deforestation. The relaxation would be part of a broader push for trade deals with developing countries that the government is pursuing in the wake of Brexit. The UK wants to join the Comprehensive and Progressive Agreement for Trans-Pacific Partnership (CPTPP), which includes Malaysia, by dropping generic trade tariffs. Negotiations began under the former trade secretary Liz Truss, who is running as a Tory leadership candidate. However, the removal of tariffs without any green strings attached would undercut the UK’s parallel efforts to end illegal deforestation overseas, one of the centrepieces of the deal that ministers forged at the UN Cop26 climate summit in Glasgow last year. Sam Lawson, the director of the UK campaign group Earthsight, who has spent many years investigating deforestation for palm oil in Malaysia, said: “This proposal to slash tariffs on Malaysian palm oil without any conditions regarding the devastating deforestation those imports are known to cause is utter madness. Instead of addressing the cost of living crisis, this government is using it as a hollow excuse for ditching its own climate goals in a craven effort to get another trade agreement under its belt.” The UK’s Environment Act, which was passed last year, makes provision for due diligence when companies import goods, including palm oil, from overseas countries where deforestation is rife. The Department for Environment, Food and Rural Affairs is currently consulting on the exact form this due diligence will take in practice. If import regulations are relaxed for Malaysia without due diligence safeguards in place, it could give countries where deforestation is happening the hope of avoiding any of the sanctions provided for in the Environment Act, rendering the government’s green pledges toothless. Countries such as Indonesia and Brazil would be likely to press for similar deals, according to campaigners. The Guardian has seen a strongly worded letter to Trevelyan from Zac Goldsmith, an environment minister and member of the House of Lords, querying her stance. He cited research showing that liberalising trade in the way the Department for International Trade (DIT) is considering for Malaysia would yield an economic benefit of only about £1.38m for the whole of the UK. “If we go for the full liberalisation, we are choosing to U-turn on the very core of our Cop26 messaging on the importance of forests,” he wrote. “We obviously cannot continue leading global efforts to break the link between commodities and deforestation if in our own trade policy we are encouraging the opposite.” In the letter, dated 28 June, he added: “It is clear this isn’t an authentic ‘cost of living’ decision; it is a values decision. And I am struggling to understand who we are trying to appeal to with these appalling values? Or how we are supposed to defend this entirely indefensible position, for example in Lib Dem target seats?” The DIT said it could not comment on live negotiations. A spokesperson told the Guardian: “We are firmly committed to maintaining our high domestic standards of environmental protection in trade agreements, and CPTPP includes environmental provisions to support these objectives. The UK has convened over 25 major trading countries to agree action to protect forests through the forest, agriculture and commodity trade dialogue, and is taking forward measures under the Environment Act to make it illegal for businesses to use key commodities if they have not been produced in line with local laws protecting forests and other natural ecosystems.” The production of palm oil, which is widely used in an array of supermarket goods, from cosmetics to bread, is a major cause of deforestation in many countries in south-east Asia. Attempts to encourage more sustainable production of palm oil have so far made little progress. Lawson said: “UK consumers don’t want to be associated with destroying orangutan habitat or human rights abuses overseas. The giant agricultural firms and supermarket chains involved in the trade in goods from Malaysia can easily absorb the tiny cost of ensuring this out of their own profits.” Current UK tariffs for Malaysian palm oil vary from 2% for crude palm oil to 12% for the more processed versions.