LONDON — Investment in Britain’s auto industry plummeted last year as the country’s departure from the European Union drew nearer without agreement over the terms of leaving the bloc, figures released on Thursday show.

Investment in 2018 dropped 46.5 percent from the year before, according to data from the Society of Motor Manufacturers and Traders, a British trade association.

With the Brexit debate in London and Brussels mired in disagreement and recriminations, concerns and warnings from businesses have grown louder. Uncertainty is usually bad for trade, and companies have repeatedly urged political leaders to provide clarity about the withdrawal and its likely effects on commerce.

But those pleas have generally gone unanswered, and many multinational companies have said they are ready to move operations outside Britain.