An international logistics expert has outlined seven key reasons why Britain’s EU traders should not regard the eventual implementation of Boris Johnson’s Brexit plans as inevitable.

Adam Johnson, director of Leeds-based Tudor International Freight, said the revised withdrawal deal the Prime Minister agreed with the EU last month proposed Britain left both the bloc’s Single Market and Customs Union at the end of the envisaged post-Brexit transition period, currently set for December 2020. The deal was also clearly intended to preface a mere bare bones free-trade agreement with the EU – which was unlikely to have been agreed by that point – and could see new barriers erected for British businesses trading with organisations in Northern Ireland, for example.

He said: “These plans would therefore make life for Britain’s EU traders much more costly and complex than at present, with the goods they send and receive being subject to increased documentation and checks, taking longer to reach destinations and costing more.”

Mr Johnson said, however, it was by no means guaranteed MPs would back the Conservatives’ plans following the General Election on 12 December, despite the party currently enjoying a healthy lead in most opinion polls. The seven key reasons for this uncertainty were: the election’s timing; voters’ volatility; the areas where the Conservatives seemed likely to lose seats; Leave supporters’ perceptions of the Prime Minister’s Brexit record; his image among the public generally; the impossibility of knowing which issues would be prominent during the campaign; and the impact of matters such as tactical voting.

Outlining these factors, Mr Johnson said: “This General Election will be the third in little more than four years and voters sometimes punish leaders who drag them to the polls unnecessarily, which they may be even more inclined to do when the contest takes place in the depths of winter.

“Loyalty among electors is also much more fluid than it was, with many voters now identifying more strongly as Remainers or Leavers than supporters of one party and four parties currently achieving double-figure percentages in most opinion polls, for example.”

Mr Johnson said the Conservatives also appeared likely to lose seats in strong Remain areas, such as London, parts of the south-east England and constituencies with large student populations. He said the Liberal Democrats were additionally hoping to make gains from the Tories in south-west England and the Scottish National Party to take multiple seats from them, not least because they had lost Ruth Davidson, their successful leader north of the border.

He added: “The Prime Minister will also not necessarily win numerous Labour Leave-voting seats in areas like the English north and midlands, as he hopes. Many electors who turned out to support Brexit there in 2016 tend not to vote in General Elections, some such constituencies have never elected Conservative MPs, and many of their Leave voters will not have supported the Tories in their lives. Given that Brexiters are generally older than Remainers, many of these people are thus being asked to discard long track records.

“Britain’s EU traders should also bear in mind the Prime Minister’s image among Leave supporters is another potential problem. He abandoned his initial bid to secure Parliamentary approval for his Brexit deal, in favour of a General Election, despite MPs having approved a second reading of the relevant bill by 30 votes. He failed to honour his repeated pledges to deliver withdrawal by 31 October ‘do or die’ and has extended our EU membership to the end of January, despite saying he would rather die in a ditch than do this.”

Mr Johnson said a further possible issue was the Premier’s image among the public overall. He was the first Prime Minister in 80 years with a negative approval rating – generally about minus 18 per cent – after only three months in the job. It was also uncertain how many people would be convinced by this old Etonian’s positioning as on their side against the so-called elite, for example.

He said: “It could additionally damage the Conservatives if voters choose to focus on issues other than Brexit. Despite the government having pledged to spend more on the NHS, schools and police, they’re blamed by many – including in those Labour-held Leave seats – for nine years of austerity, for instance. Public spending is also a topic on which other parties tend to have natural advantages in voters’ minds anyway.”

Mr Johnson said a final huge unknown was the potential impact of tactical voting, electoral pacts – such as the so-called Remain Alliance, comprising the Liberal Democrats, Green Party and Plaid Cymru – and individual candidates standing down in favour of others.

He said: “For all these reasons, Britain’s EU traders shouldn’t regard implementation of the current draft withdrawal deal as a foregone conclusion. Other options, including a renegotiation of the agreement, a confirmatory referendum, and even Brexit being cancelled altogether, currently remain very much in play.”