Eurostar trains may stop running in the event of a chaotic no-deal Brexit, the French minister for Europan affairs has warned.

Nathalie Loiseau sounded the warning as she made clear France was against a “blindfold Brexit”, in which key negotiating issues were deferred until the UK had left the EU.

Speaking in London, Loiseau coupled a firm commitment to protecting the single market with a frank warning that France would pass emergency legislation within weeks to protect its citizens from the impact of Britain leaving the EU without a deal at the end of March.

She said there was a real possibility that, in the absence of any contingency plans, Eurostar trains could be stopped on reaching French territory, and planes from Britain could be prevented from entering French airspace.

“This is the reason we must prepare for a no deal because we cannot wake up on 30 March and tell our businesses and citizens: ‘Well, we thought it would never happen, so we are not ready.’”

Loiseau also set out France’s resistance to a blindfold Brexit in which the EU and UK would fudge a deal on “future relations”, deferring difficult issues until after UK had left and the 21-month transition had begun.

She told the Chatham House thinktank: “We have to have a clear sense of the balance of rights and obligations on the future relations between the UK and the EU27. Details will be worked out afterwards, but it would be to the benefit of neither the UK or the EU27 to remain vague on what is going to be our future relations at the moment of leaving.

“There is a need for clarity and perspective for our fellow citizens, for our businesses,” she said, adding it would be irresponsible to do otherwise.

There have been reports that Germany favours a fudged political declaration on future relations, partly due to the lack of time and a fear that Theresa May will be toppled by Conservative sceptics bent on rejecting any deal.

The final deal will include a legally binding withdrawal agreement covering the Irish border and a declaration on future relations.

Loiseau said those who had suggested the significance of the Irish border was being exaggerated were being irresponsible. Defending the need for a legal backstop aimed at avoiding a hard border, she said “we cannot wake up on 30 March to tell our Irish colleagues we don’t have a solution and we must go back to a hard border”.

She said the UK and the EU had been trying to divorce without hurting the kids, but “there is no way that this can be a win-win situation for both parties”.

She rejected requests to speculate on a possible extension of the talks beyond March, saying no such request had come from the British government or parliament. “Should there be a new position we would study it,” she said.

Loiseau said the goal remained an ambitious, unprecedented agreement, but this could not involve the EU changing the principles that govern the single market.

Ministers in the UK have been particularly concerned to ensure that planes will be able to fly to EU countries in the event of no deal being reached. The Department for Transport incurred the wrath of the EU’s chief negotiator, Michel Barnier, this week after writing to individual member states to try to strike a side deal on the issue.

While the UK has been keen to outline the risks of no deal for areas ranging from driving licences to passports, Downing Street downplayed the warnings from the French minister.

When asked to respond to her comments about planes and the Eurostar, the prime minister’s spokesman said: “It’s not in anybody’s interest for that to happen.”

The UK believes that countries such as Spain will not want to jeopardise revenues from British tourism, and that they would, if necessary, be prepared to strike bilateral deals to maintain transport services if there was no prospect of a deal.

A Department for Transport spokesperson said: “Our ambition in the upcoming negotiations with the EU is to maintain the existing liberal level of transport access.

“Both the UK and the EU reap significant benefits from the arrangements currently in place and it is in no one’s interests for planes and trains to be ‘turned away’.

“We are confident of reaching an agreement with the EU on transport access but we continue to make sensible contingency plans, including exploring bilateral arrangements with member states.”