Whatever happens in the Brexit negotiations, the question of the UK’s future trade relations with countries outside the European Union will become acute for businesses, investors, workers and citizens.

In the immediate term, the overriding UK objective will, of course, be to secure continued access to the EU market. Larry Elliot argues in the Guardian that EU membership has not coincided with significant growth of UK exports to the EU. So what? Without EU membership, it is extremely unlikely that UK exports would have reached even today’s levels – that 80% of UK production of motor vehicles would be exported, mostly to the EU. Elliot also argues that “since the late 1990s, a deficit in goods with the EU of £6bn a year has ballooned into a deficit of £95bn a year”. But this has nothing to do with tariffs (or the absence thereof); it’s to do with the ever-shrinking UK manufacturing base and a low savings rate. Italy now produces 50% more manufactured products than the home of the industrial revolution.

Membership of a community of nations brings more clout to the table than when acting on behalf of a medium-sized country

In 2016 the then Brexit secretary, David Davis, announced that Britain was moving quickly towards radiant horizons on a trade deal with the US, along with China, giving us “a trade area almost twice the size of the EU”. Like many Brexiteers, his conviction seems to have been that EU membership, including membership of the customs union, has held the UK inside a bloc that was unable or unwilling to strike major trade deals with “third” (non-EU) countries. These Brexiteers were, in the words of Jonathan Freedland, “itching to shake off the shackles of Brussels and run into the embrace of the ‘Anglosphere’”.

But has EU membership truly hampered the UK’s ability to export its goods under advantageous terms? From the formal perspective, if Britain leaves the EU customs union, it will be at liberty to negotiate new free trade agreements (FTAs) with non-EU countries. .

But how will it lower trade barriers with these countries? And will this be easier, objectively speaking (that is, without a pro- or anti-Brexit prejudice), than it has been inside the EU? The short, objective answer is no.

Membership of a community of nations, negotiating with one voice, brings much more clout to the negotiating table than when acting on behalf of a single medium-sized country. When negotiating on behalf of 500 million people, if the EU says no it is no, and if it says yes, the yes brings access to the world’s biggest market, and to the non-EU countries concerned.

UK export interests are highly specialised: financial and other services, industrial products such as pharmaceuticals, aerospace and motor vehicles. However, opening up overseas markets for services is difficult at best – as even the EU, with its much greater negotiating power, has discovered. Why should the UK succeed where the EU has not? As for industrial products, top UK exports such as aircraft and medicine are subject to virtually no tariff barriers in (potential) major UK export markets. The car industry is subject to significant tariffs, but why, for instance, should the US accept the elimination of tariffs in this industry when virtually all UK production is controlled by EU and Japanese companies?

Former Brexit secretary David Davis. Photograph: Simon Dawson/Reuters

UK agriculture is currently protected by relatively high EU tariffs. If these were to be significantly reduced or eliminated under pressure from the US, Canada, New Zealand or Australia, the outcome would be a disaster, especially for the livestock sector. EU membership has protected UK farmers as much as their much-derided counterparts in “Europe”. It is difficult to see how this basic problem can be overcome in negotiations with countries, especially the US, that have always put food and agriculture at the top of their wish list.

There are, however, a number of countries with which it should be possible for Britain to conclude FTAs within a short period of time, namely those with which the EU28 has already done the work by negotiating such agreements. Since the UK was part of the EU at the time when these agreements were concluded, there is no economic reason why it should not be possible to adopt a copy-paste type approach and “carve out” FTAs with, for instance, Norway, Switzerland, Chile, Mexico, Japan, Canada, not to speak of Turkey (with which there is a customs union), as well as others of lesser importance. UK market access to those countries would in substance be exactly as it is today. Plus ça change …

The most difficult obstacle will be achieving access, via an FTA, to the US market. UK negotiating power will be limited, and the key UK interest – opening up the US financial market and those for other services – has always been strongly resisted by the US.

American demands are also extreme. A list just published by Washington makes this abundantly clear, and is highly recommended reading for concerned citizens. Some of the jargon is only intelligible to “experts” but most objectives are transparently, sometimes touchingly, self-centred and blatantly focused on “take”, explicitly rejecting any “give”.

Yet others US objectives are, to put it mildly, surprising. For instance, an entire page enjoining the UK to observe stringent labour standards, and another devoted to the environment (without a single word on climate change). No trace here of a “special relationship”. Accepting these demands would be tantamount to becoming the 51st state on economic questions without the right to vote. Of course, no UK government would ever accept all this, but its rejection will, by definition, also make the US reject opening any markets of interest to the UK.

Consider a few examples: the US wants a sharp reduction of tariffs on agricultural products, access for hormone-treated beef (which is banned by the EU on health grounds), chlorinated chicken, genetically modified organisms, and higher prices for US pharmaceuticals currently kept under control by the NHS. When the US has pressed the EU on these issues in the past, the UK government (with the backing of civil society in the UK) has always supported the European commission in rejecting these demands.

In the unlikely event that an agreement becomes useful and doable, who would want to conclude an FTA with a country whose president has denounced three much more important international treaties and violated basic World Trade Organization rules? What investor would want to risk their money on such a shaky basis?

Agreements with the former UK dominions, Australia and New Zealand (Canada was mentioned above), remain. The sentimental value is perfectly understandable. These are countries with which the UK has close cultural and emotional ties, and many experienced a shock, and there was much ill feeling, when trade was negatively affected by the UK joining the EU.

The economic importance is limited, but the political and emotional value is great. Here, applying the proverbial common sense left over from the Brexit psychodrama should make it possible to reach agreement without major problems. In agriculture, Australia is facing climate-induced physical limitations on its export capacity, and therefore on its interest in pushing the UK beyond a certain point, and New Zealand has always demonstrated a very “European” approach to such negotiations, realising that any agreement has to be to the mutual advantage.

The perceived advantages of leaving the European flock to negotiate free trade deals left and right will turn out to be like the mirage experienced by travellers in the desert, mistaking an accumulation of hot air for an oasis. The next election may show whether voters appreciate being taken for camels.

• Mogens Peter Carl was European commission director-general for trade and subsequently environment