The Brexit vote means that trade is now a top priority for the UK for the first time in decades, but markets have reacted badly over the past fortnight as it becomes clear that ministers have, as of yet, no clear plan for renegotiating the existing trade deals that Britain has with more than 60 countries throughout the European Union, or for trade negotiations with the bloc itself.

If ministers repeat the mistakes of the past, in particular those made during negotiations between the EU and the United States on the Transatlantic Trade and Investment Partnership (TTIP), then Brexit will fail and the new trade deals that Britain needs will simply not work for businesses, workers or consumers.

I set up and chaired the All-Party Parliamentary Group on EU-US Trade and Investment until last year. The group helped to scrutinise the troubled transatlantic deal and led the only Commons debates held over two years on the negotiations. Here’s how the biggest pitfalls can be avoided.

First, transparency and accountability. Suspicion about TTIP grew because the public felt locked out. Worryingly, the government has already said that it would give “no running commentary” on the Brexit negotiations, or give parliament a vote. Instead, ministers should ensure that their aims are published and debated in parliament before talks begin, and that proposals are published as negotiations go on, just as the European Commission has been forced to do on TTIP.

Second, involvement. Ministers should ask the public what they want from trade. Talk with small and mid-sized companies, trade unions and local communities. Draw up the principles of trade deals by drawing on these views. This isn’t just good politics, but the only way for ministers to know truly which trade barriers are a problem, where regulatory change would undermine standards or open up opportunities, and where their negotiating attention needs to concentrate.

Third, communication. The potential of trade must be put in plain terms. How many Melton Mowbray pork pies could be sold in the US if the regulator there recognised British freeze-dry technology as safe? How many more jobs could be created if British-made cars did not have to meet American safety standards, when they already pass equally stringent tests in the UK? Citing GDP growth gains or overblown macro-estimates — as David Cameron did when he claimed that TTIP would bring a £10 billion boost to jobs and prosperity — leave the public cold.

Fourth, trade must be fair and seen to be fair. Suspicion about trade deals on both sides of the Atlantic is rising because politicians and trade negotiators haven’t been able to persuade people that there will be more jobs for them and their communities. The gains from trade are not equally shared across sectors or regions of the country. The publication of a “regional gains test” or impact assessment would help to show area-by-area benefits and risks.

Finally, any trade deals must protect public services. The ambivalence and ambiguity from government ministers over concerns about the NHS during the TTIP negotiations was deeply damaging. At no point did ministers give the same clear commitment that the health service would be fully protected that I secured, first in face-to-face meetings then in writing, from the EU’s chief negotiator. The public will expect upfront exemptions for public services, especially the NHS, in black and white, and the government must give that reassurance.

If ministers learn from these five failings on the transatlantic trade pact, they may get the public and political support to negotiate better deals that post-Brexit Britain needs.