Negotiations must at each stage involve business, unions and civil society groups, as well as face in-depth parliamentary scrutiny, the letter adds.
The Confederation of British Industry, the Trade Justice Movement, National Farmers Union, Greener UK, the Federation of Small Businesses, Make UK, the British Chambers of Commerce and the Scottish Chambers of Commerce are among the signatories.
The intervention, which comes ahead of the G7 summit in Cornwall next week, warns that ministers “will not meet their ambitions for the economy” if they fail to set out a clear policy framework for trade.
Transparency of approach
A Government source last night insisted Ms Truss had been transparent about her approach and pointed to her remarks at a keynote speech at Chatham House last October.
She said then that her attitude towards trade was rooted in Britain’s “values of sovereignty, democracy, the rule of law, and a fierce commitments to high standards”.
The UK will work with like-minded democracies to support freedom, human rights and the environment while boosting enterprise through lowering barriers to trade, the International Trade Secretary added.
The Government source said ministers had also been robust on red lines in trade deals, including removing the NHS from the negotiating table and refusing to compromise on high standards in areas such as food production.
In a report, entitled Trade for All, published on Wednesday and backed by the coalition of groups, the Government is warned that it is at risk of missing out on a range of opportunities from post-Brexit deals if it focusses on short-term gains.
Co-author of the paper Emily Jones, associate professor of public policy at the University of Oxford’s Blavatnik School of Government, said ministers must adopt an approach that helps “harness the opportunities of the digital economy, tackle climate change and achieve the UN Sustainable Development Goals, including sustainable post-Covid recovery”.
Chris Southworth, secretary general of the ICC UK, said: “It’s time to overhaul the UK’s stance on international trade so that we don’t miss out on these benefits.
“We will deliver far better outcomes from trade if we are all aligned and working together. To do that, we need a framework we can all buy into and support.”
Mounting concern over UK-Australia trade deal
It came as campaigners voiced concerns that an imminent UK-Australia trade deal could allow Australian companies to sue the British government through a system of secret courts for taking action on the environment or workers’ rights.
Nick Dearden, director of Global Justice Now, expressed alarm about an investor-state dispute settlement system being included in the forthcoming pact, which he alleged could allow companies to sue the Government through a corporate tribunal system when they believe policies have harmed their profits.
“These courts would allow Australian companies to extract eye-watering pay-outs from the government for taking action on anything from climate change to workers’ rights.
“The Australian company behind the Cumbrian coal mine could sue our government in an exclusive, secretive tribunal for halting or delaying the project for environmental reasons. Right now, the Dutch government is being sued in these courts for daring to phase out coal power, so we know fossil fuel companies won’t hold back.”
The Government declined to comment on live negotiations.