French businesses working with British contractors or suppliers should now be actively seeking out alternatives, the French government has said, as it further ramped up preparations for a no-deal Brexit that it sees as increasingly likely.

“Let’s not panic, but let’s prepare for different scenarios,” the Europe minister, Nathalie Loiseau, said on Friday as she unveiled a 28-page booklet for companies with British ties, which advises them to adopt the UK’s wartime motto and “keep calm and carry on”.

Companies reliant on UK business partners should explore other options outside Britain, while those with UK-based operations in specific EU-regulated sectors such as pharmaceuticals should think about moving them to the continent, the guidance says

Last week France triggered a €50m (£44m) plan for no-deal after the UK parliament overwhelmingly rejected Theresa May’s proposed deal. The French prime minister, Edouard Philippe, said there were now “strong fears” that Britain could crash out of the EU without a deal on 29 March.

The government authorised new infrastructure spending on border checkpoints, roads, lorry parks and warehousing at ports and airports and is hiring 750 extra staff, including customs officials and veterinary and standards inspectors, to carry out checks on goods, livestock and food products.

Agnès Pannier-Runacher, the junior economy and finance minister, said on Friday that France was “hoping for the best but planning for the worst”, and that no-deal would plunge the country into an “unprecedented situation with a major trading partner”.

The risk of no deal had “significantly increased”, she said. “There is absolutely no time left to lose for these companies. The countdown has well and truly started.”

The booklet says French firms with financial services contracts in the UK should think about switching them to an EU27 country and consider what to do with confidential data currently stored in Britain. Those with UK-based employees should start thinking about possible social security issues and consider hiring temporary staff. It also suggests that French companies working with UK partners on programmes funded by the EU should start searching elsewhere for collaborators.

As many as 30,000 French companies export to the UK, and 3,300 have British-based operations, according to government figures. French officials plan to hold around 30 meetings around the country to help small businesses in particular prepare for all possible forms of Brexit.

Loiseau said Paris would of course be looking for a “close and mutually beneficial” relationship with Britain after Brexit, but deal or no deal, it would necessarily be one that was “downgraded” from its current status.

“There is no relationship more simple, more profitable, more complete – between businesses, between citizens – than being a member of the European Union,” she said.