The experts always said Brexit would mean paperwork. On Wednesday the two sides of the negotiation proved the point by issuing a flurry of explanatory documents through social media in a spat that swiftly came to be called “the slide wars”.

The unseemly Twitter row was provoked by a post from the Downing Street press office late on Tuesday evening in which the British government gently mocked the EU’s chief negotiator, Michel Barnier, for his attachment to a slide first produced in 2017.

That document suggested that only a Canada-style trade deal would be on offer to the British government – then led by Theresa May – if it rejected free movement, regulatory alignment, a customs union and the jurisdiction of the European court of justice. “Now they say it’s not on offer after all,” the No 10 press office account tweeted. “Michel Barnier, what’s changed?”

No.10 Press Office (@Number10press) In 2017 the EU showed on their own slide that a Canada type FTA was the only available relationship for the UK. Now they say it’s not on offer after all. @MichelBarnier what’s changed? pic.twitter.com/ve8zeAqbSZ

Boris Johnson has railed against the EU’s suggestion that there needs to be continued alignment between the UK and Brussels on state aid rules and environmental, social and workers’ standards to avoid either side receiving a competitive advantage under a new free trade deal.

The prime minister is seeking looser so-called level playing field arrangements, similar to those contained in a deal struck between Canada and the EU.

EU sources described the British as “deeply dishonest”. The European commission’s UK taskforce was quick to mobilise its social media accounts. A slide was published illustrating the uniquely high level of trade between the EU and Britain and pointing out the close geographical proximity of the UK to the European coastline.

“There must be robust level playing field safeguards to avoid unfair competitive advantages in social, environmental, tax and state aid matters,” the commission document said. “This is not new. The UK government – and parliament – agreed this with the EU’s 27 member states less than six months ago. Each agreement with a third country depends on a number of different factors, including distance and the level and intensity of trade we have with that particular country (see attached slide).

“All these factors matter and determine the content of the agreement. Therefore, comparing the situation of the UK to other countries, such as Canada, simply does not work.”

Negotiations between the UK and the EU are due to start in the first week of March. Diplomats in Brussels are still working on the EU’s final negotiating position.

Asked about the row, Barnier told reporters he had “no time for controversies”.

A UK government spokesman said: “We are clear we are not asking for a special, bespoke or unique deal. We want a Canada-style free trade agreement, which the EU has frequently said is on offer.”