I discovered the prime minister’s stance on trade deals and agriculture by accident. Boris Johnson had given a typically rambling speech, at the start of the month, in which he promised a science-based approach, rather than “mumbo-jumbo”. It was a banal assertion – who doesn’t prefer science to superstition? As such, it was unremarkable. Johnson is famous for his unpreparedness; there’s even something soothing about his flimflam. The more meaningless his assertions, the less likely he is to take concrete action on them.

What we have yet to develop is any strategy for opposing negative or mixed outcomes

Yet people who know about agriculture and how it relates to international trade were alarmed. The so-called science-based approach is US-speak for a regulatory system that assumes a method is legal unless it has been proven unsafe. The EU takes the opposite approach, which it calls not “mumbo-jumbo” but “the precautionary principle”: a method or substance is not legal until it has been proven safe. The vast discrepancies between the two trading blocs on animal welfare, genetic modification, pesticides and chemicals, and hormones and antibiotics used on livestock are rooted in this dichotomous interpretation of what safety means. Johnson was therefore implicitly allying himself with the US rather than the EU.

The consequences for UK agriculture would be devastating if this became policy. Farmers would either have to adopt American methods in order to compete, whereupon they would no longer be able to sell into the EU; or they would have to accept an influx of cheaper American produce and effectively give up on their own nation’s market. It makes a mockery of the drive to reduce food miles; it has horrific connotations for animal husbandry; it drives farming towards an industrial model at a time when we need a land-use revolution in precisely the opposite direction. And I found that out looking up chlorinated chicken. A fortnight later, an interviewer on the Today programme referenced the prime minister’s “science base” with no understanding of its subtext; a casually dishonest government has a lot of space to play in when our working knowledge of the jargon is so low.

Yet there are very good reasons for ignorance, not just of the language of trading regulations, but of the democratic levers at our disposal for opposing damaging and deleterious deals. Trade deals are commonly conceived as a set of tariffs, which civilised, commercial nations can barter down to their mutual advantage. In reality, especially between developed nations, they cover intellectual property provisions, regulation of business and finance, public procurement – with huge implications not just for the rights of consumers and workers but for the distribution of public money and the delivery of public services.

The immediate democratic deficit is that parliament has very little power over them, and once they’re passed they have the status of international law, so a future government cannot simply overturn them. MPs have no power of veto. Their only scrutinising power is that laid down by the Ponsonby rule of the 1920s, which allows for a debate between signing and ratification. This was beefed up slightly in 2010 to give that debate statutory weight, but all they can do is delay any deal rather than stop or amend it.

Play Video 1:38 'There is no need for a free trade agreement': Boris Johnson outlines UK stance after Brexit – video

This has persisted in large part because of our membership of the EU. Arguably, had we never joined in 1973, the arc of progress would have demanded greater accountability and transparency, and our system would have evolved to look more like that of the US, where they need two-thirds approval from the Senate before a treaty can be signed. Instead, we folded our decision-making into that of the European commission. Trade justice campaigners spent decades criticising the commission for its neoliberal agenda, often with very good cause: yet the EU’s system of oversight far excels anything devised by the UK parliament. Every MEP gets access to all negotiating texts. The European parliament can raise objections and must be heeded. They have a right of veto and have used it, often responding to public protest, as against the Anti-Counterfeiting Trade Agreement.

Individual member states, and even regional parliaments, can have a decisive impact on the terms of deals whose scope is much larger than the region itself. Famously, the Belgian parliament of Wallonia forced significant concessions on both agriculture and transparency during the negotiation of Ceta, the trade deal with Canada.

As members, we were always at the freest end of the trade spectrum and rarely even considered the regional impacts of any given deal on the UK. But we benefited nonetheless from such accountability as was embedded in the institutions. The muscles of our national parliament became completely atrophied over the period. Even if you could imagine tens of thousands of people taking to the streets to protest against a free trade agreement with the US, there would be no mechanism to connect that anger to representation. There is no presumption of transparency: in a case brought against the government last Friday, it transpired that talks have begun with at least one unknown country, whose details have been deemed too sensitive for publication.

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It pleases Liam Fox and his successors to describe these agreements as unalloyed blessings, lucrative contracts won by plucky business. In reality, no trade deal is completely neutral in impact. There is always an implication for jobs or rights or wages or competitiveness, and the glacial pace of large cross-continental deals reflects the complexity of off-setting harm in an agreed and open way. That much we have picked up from the past four years. What we have yet to develop is any strategy for opposing negative or mixed outcomes, in the absence of any clear role for parliament. It will take large-scale alliances across sectors, and the same solidarity between unions, not to mention intense civic scrutiny. However powerless we feel under an executive that is unfettered by oversight, that’s nothing compared to how powerless we will be once any deal is signed. Sovereignty, huh? Who knew it would be such hard work?

• Zoe Williams is a Guardian columnist