PARIS (AP) — France's main business federation says Britain's Oct. 31 departure from the European Union shouldn't be delayed again unless there's a major shift in negotiations, warning that "a Brexit without end" would be economically damaging.

The MEDEF federation advised Tuesday that all French businesses should continue to prepare for a so-called "hard" Brexit, without a deal to cushion expected jolts to European economies and firms.

In a statement, MEDEF said it is "seriously concerned by this situation and its harmful consequences for all European citizens and companies."

But it also said that only "major political reasons" could justify the EU granting another Brexit extension. It said the EU should not "fall into the trap of a Brexit without end, sterile for our economies and dangerous for the integrity of the union."

British Prime Minister Boris Johnson says Britain must leave the European Union at the end of October, with or without a divorce deal smoothing out post-Brexit trade. But many lawmakers fear a no-deal Brexit would be economically devastating, and are determined to stop him.

France's government is preparing for a no-deal Brexit on Oct. 31 anyway, and has trained 600 new customs officers and built extra parking lots arounds its English Channel ports to hold vehicles that will have to go through extra checks if there is no divorce agreement.

The French minister who oversees customs, Gerard Darmanin, said Tuesday he's worried that the British side isn't ready.

"You are asking me how our British friends have prepared themselves: we don't know and we have a few question marks about it," he told legislators.

He said the French government is holding seven test runs over the coming weeks to ensure that the extra border measures are working, noting that 4 million trucks cross the Channel every year through the Eurotunnel and on ferries.