Nathalie Loiseau listed the Eurostar problem among others that could occur between the UK and France in the event of no deal.
Brexit no-deal may stop Eurostar trains entering France says French minister
Eurostar trains heading from London to Paris may not be allowed into France if there is no Brexit deal and sufficient preparations have not been made, France's European Affairs minister said on Thursday.
Nathalie Loiseau was asked at a speaking event in London whether it was a real possibility that Eurostar trains coming from London would not be allowed on French soil if there were no Brexit deal.
"If we do nothing, and if we reach no agreement, this is what would happen among other examples," she said.
"We cannot wake up on March 30 and say to our fellow citizens and to our business: 'Wow we thought it would never happen so we are not ready.'"
She said France was ensuring it was ready for any eventuality.
"I will go to the French parliament in the coming weeks with a draft bill so that we get prepared for each and every scenario," she added.
The comments could mean bad news for the Eurostar company, which opened its new London to Amsterdam service in April this year. Until now it has been growing well, recording a preliminary operating profit of £57.6m for 2017, increasing sales revenue by 11% from 2016.