Last week, the government set out key elements of its strategy for achieving Britain’s withdrawal from the European Union. It seeks a soft landing to a hard Brexit. It wants a time-limited transition period after March 2019, when Britain is due to leave the bloc. During that period, the government hopes for a “close association with the EU customs union”. When it ends, Britain will leave the customs union but seek “a new customs arrangement” that preserves “the freest and most frictionless trade possible” and Britain will then seek a free trade agreement.

These proposals are beset with ambiguity and difficulty, although the idea of a transitional agreement has been welcomed by business. Brexiters fear – and some Remainers hope – that at the end of the transitional period it will be found to have been so comfortable that it will be extended. In that case, Britain would, to a significant degree, remain in the EU, but as a de facto satellite rather than a participating member.

Remainers put too much faith in the transitional agreement. Business seeks certainty so that new investment can be undertaken without fear that market conditions will radically alter. A transitional agreement cannot provide this. It merely offers a stay of execution. A company seeking to decide whether to invest is not helped by being told that the period of uncertainty, instead of being 18 months, will be prolonged for a further two years.

But business also seeks a business-friendly final agreement. That also seems problematic. If Britain seeks merely a free trade agreement, it would be natural for her to join the European Free Trade Association, which Britain left when she joined the EU in 1973. But that does nothing for services nor for the non-tariff barriers that constitute so important an element in modern international trade.

That is why, of the four Efta members, three – Iceland, Liechtenstein and Norway – are also members of the European Economic Area, which involves, in return for access to the internal market, accepting the principle of free movement, together with many of the laws of the EU.

The fourth member of Efta – Switzerland – is not a member of the EEA, but has a series of about 120 cumbrous bilateral agreements with Brussels so as to secure access to the internal market. These agreements require the transposition of European Union law into Swiss domestic law, so that Switzerland too accepts many of the laws of the bloc.

Turkey, which perhaps enjoys the kind of “close association” with the EU customs union that the government has in mind, has a customs agreement with Brussels. But, when the bloc signs a free trade agreement with a third country, Turkey’s markets are opened to that third country and so those same countries have no incentive to sign separate trade deals with her.

The third country’s markets, however, are not necessarily opened to Turkey – because she is not a member of the EU and Turkey has no vote on the union’s trade or commercial policy. She has to submit to regulation without representation. Turkey does not even receive, in return, frictionless trade, as anyone who has seen the queues of lorries at the Bulgarian border – some 1,000 trucks a day, gridlocked, with their drivers cursing the seemingly endless paperwork – can testify. Turkey, therefore, is not a model for Britain, but a warning.

The British government, however, favours a bespoke free trade agreement, one specifically tailored to British needs. What the negotiators hope for is an agreement offering some of the advantages of the customs union and the internal market without the obligations of EU membership. In Giuseppe Tomasi di Lampedusa’s novel The Leopard, the hero’s nephew, Tancredi, declares that everything needs to change so that everything can stay the same. The negotiators would like Britain’s obligations to the EU to change while the benefits stay the same.

It is not clear why Brussels should agree to such an arrangement, which will seem to the member states to be a form of reward to a member state that is leaving because it no longer wishes to pay the subscription or accept the obligations attached to membership.

The EU does not have a frictionless customs border with any country outside the single market or customs union. Indeed, Michel Barnier, the EU commission’s chief negotiator, confirmed last week that such an arrangement was not logically possible and the bloc has not so far allowed any country to obtain the benefits of the internal market or the customs union without imposing obligations in the form of obedience to EU laws.

Theresa May, it is often forgotten, was a Remainer in 2016 and inherited a crisis not of her making. She has now secured a document around which the various elements in her cabinet can unite. But, inevitably, the real choices are obscured. For unless Britain is prepared to accept EU laws that she has no role in formulating, there seems no middle way between accepting the logic of Brexit, which means leaving the internal market and the customs union or remaining.

The Brexiters, however, hope for benefits outside the EU. For many Conservatives, the logic of Brexit was a resurrection of Thatcherism. They wanted Britain to become a free trade global hub, purged of tariffs, subsidies and regulations, a European Singapore. But whatever the merits of that solution, the election has clearly shown that there is no majority for it in the country.

Other benefits sought by Brexiters may be slow in arriving. Trade deals with third countries will take time to negotiate, as Liam Fox, the international trade secretary, discovered when he stepped into a controversy over chlorinated chicken while in Washington; and, whatever the merits of the American system of separation of powers, it does not make for speedy congressional ratification of treaties. Meanwhile, the cheque for the £350m a week for the National Health Service promised in the referendum seems to have been lost in the post.

The election showed that Brexit continues to divide the British people. Some have argued that the country is united around it since 87% of voters – the total percentage of votes cast for the two major parties – supported parties favouring Brexit. But that is absurd. For, clearly, many Remainers voted Conservative or Labour and there is evidence that the swing to Labour was caused in part by Remainers seeking revenge.

The truth is that both Conservatives and Labour are divided on Brexit. The majority of MPs and the majority in the cabinet voted Remain. For this reason, whatever the outcome of the negotiations, the government might find it difficult to secure parliamentary support for the deal. Indeed, it might have to rely on Labour votes to achieve it. The angst that this would cause could lead to serious ructions in the Conservative party. In March 2019, therefore, Tories may well come to the view that there is a stronger case for another referendum than they currently believe.

In the New Statesman, George Eaton argues that to hold another referendum would show disrespect to those who voted last year by 52% to 48% for Brexit. However, Nigel Farage told the Daily Mirror on 16 May last year – 38 days before the referendum – that “in a 52-48 referendum this would be unfinished business by a long way”. The BBC quoted him as saying that “there could be an unstoppable demand for a rerun of the EU referendum if Remain wins by a narrow margin”. “Win or lose this battle,” Farage declared, “we will win this war.”

Brexiters can hardly deny to their opponents the same democratic right that they claim for themselves, unless they secretly fear that the British public has, in fact, had second thoughts. The sovereignty of the people, after all, did not come to a sudden end on 5 June 2016. Finality, Disraeli said, is not the language of politics.

By March 2019, the outlines of the deal should be reasonably clear, since the withdrawal agreement is required to take into account “the framework of its future relationship with the union”.

That framework will need to be approved by parliament. But it can be legitimised only by the people through a referendum, which would either endorse it or show that voters no longer wished to leave the European Union.

Vernon Bogdanor is professor of government, King’s College, London