A key slogan for the UK’s ruling Conservatives in the December general election is the promise to “Get Brexit done”.

Boris Johnson says by winning a majority, parliament will then pass his divorce deal to take the UK out of the EU on January 31 next year. The prime minister is appealing to voters by arguing that the country can then move onto other issues.

But his critics point out that the process to determine future UK-EU relations will only just be starting – and this risks being far more complicated.

They accuse the government of being disingenuous in arguing that a trade deal with the EU is attainable next year. If no deal is agreed by then, the UK and the EU will trade on World Trade Organisation (WTO) terms.

This would bring an abrupt change to EU-UK trading relations which many business organisations and trade experts argue would cause cross-border disruption and higher prices.

What sort of EU trade deal is Boris Johnson aiming for?

In a video posted on Twitter last weekend, Johnson reiterated the government’s aim: “to do a big free trade deal with our EU friends and partners… not based on any kind of political alignment”.

Johnson says the deal the UK will aim for will be “on the model of a super Canada plus arrangement”.

Canada’s free trade deal with the European Union (known as CETA), which came into provisional effect in 2017, took seven years to negotiate and runs to almost 1,600 pages. It will take several more years to implement fully.

The CETA agreement eliminates most tariffs on goods but does not remove regulatory barriers. Canada is not in the EU’s single market so its products still undergo border checks, although the use of technology is encouraged to speed up customs procedures.

There are provisions for mutual recognition in services, a sector representing most of the UK economy. However, Canada’s financial services do not get “passporting” rights to operate across the EU.

Boris Johnson set out his “Super Canada” Brexit plan in September 2018 – saying it would involve zero tariffs and quotas on all imports and exports, mutual recognition of standards, technological solutions, and would cover goods and services.

What are Johnson’s chances of striking this trade deal in 2020?

After January 31, the UK will have only 11 months to negotiate a free trade deal with the EU – compared to the seven years it took Canada to strike its agreement.

Johnson and his supporters highlight the speed with which the government agreed a new EU withdrawal agreement. This was struck with EU leaders in October – but only after the prime minister abandoned a key part of his earlier strategy over Northern Ireland.

Under the terms of the deal, once the UK leaves the EU a transition period will run until the end of next year, keeping UK-EU arrangements largely as they are now.

Even if the UK does leave the EU with a deal in January, another “cliff-edge” would soon loom over the horizon. A decision on whether to extend a transition period beyond its expiry date of December 31, 2020 would have to be taken by July.

Boris Johnson insists that a trade deal can be done during the transition and has ruled out extending the transition. This was a key factor in Nigel Farage’s decision to stand down his Brexit Party candidates in Conservative-held seats, to avoid splitting the pro-Brexit vote at the election.

“We can get a fantastic new free trade agreement with the EU by the end of 2020. And we will not extend the transition period beyond the end of 2020. There’s absolutely no need for that,” Boris Johnson said in his campaign video.

The European Union’s guidelines on negotiating trade agreements say “reaching an agreement usually takes several years”, and involves over 30 stages.

These include interaction in the negotiating and decision-making process between the European Commission (the EU’s executive or civil service), the European Council (representing national governments), and the European Parliament (elected MEPs).

As well as trade, future UK-EU relations on other matters will also have to be negotiated in this timeframe – including security, science and education.

What do the politicians say?

“Given the refusal to extend the Implementation (transition) Period beyond 2020 and the obvious lack of time to negotiate a Free Trade Agreement before then, this means we will be on WTO terms by January 2021. Leaving the IP on WTO terms would be devastating to many sectors of our economy. It’s a thoroughly irresponsible policy” – David Gauke, via Twitter. The ex-justice minister under Theresa May’s government was expelled from Boris Johnson’s ruling party for opposing his Brexit strategy. He plans to stand as an independent candidate in the December election.

“(On the prospect of no trade deal being struck) It’s a hypothesis which has been put by people… who have consistently sought to raise bogeys and to make people’s flesh creep, when the reality has been our prime minister has managed to secure a (withdrawal) deal which puts us on a path towards – not just free trade and friendly cooperation with the EU – but also good trade deals with other countries and other regional trade blocs” – Michael Gove, UK minister with responsibility for a no-deal Brexit, speaking on BBC Radio.

What do the experts say?

Lionel Barber, the outgoing editor of the Financial Times, told Sky News the idea that the UK could complete a detailed free trade deal next year, rather than a bare-bones agreement, as “fantasy”.

Peter Ungphakorn, a trade policy expert formerly with the World Trade Organisation, questions the idea of a UK-EU free trade deal “with no alignment”, and says the term “Super-Canada” – as vaunted by Boris Johnson – implies a more comprehensive agreement than the Canada-EU (CETA) deal.

“How many people know what that actually means? How many have looked at CETA’s table of contents let alone read the agreement?” he asked via Twitter.

David Henig, director of the European Centre for International Political Economy (ECIPE), argues in a Twitter thread that the details of a trade deal are highly important and “any UK exporter to or importer from the EU could be adversely affected if you get this wrong”.

Both sides, he says, have yet to consult widely or establish negotiating arrangements. Even if timescales can be managed, he argues “it is… highly inadvisable for the UK to attempt to complete negotiating a trade agreement in 2020 – without proper consultation or negotiating structure how do we know what we want to achieve?”.

Many commentators have said the UK government is failing to address fundamental questions over the country’s eventual destination as a trading nation. Some experts say the UK faces a key choice over regulatory alignment: whether to stay close to EU rules to access the European market, or follow American regulation.