Nissan's boss has said decisions about any future investments in its British operations are being put on hold until more details emerge about the terms of the UK's Brexit deal with the European Union.
Nissan's Sunderland plant built nearly one in three of Britain's 1.6m cars last year - however, most of the site's output is exported to the rest of Europe.
"The question is what's going to happen in terms of customs, what's going to happen in terms of trade, what's going to happen in terms of circulation, particularly of the products," Renault-Nissan Alliance chief exec Carlos Ghosn told the BBC.
"All of these are very sensitive elements that are going to determine, how and how much we are going to invest in the UK particularly for the European market."
Ghosn added that the Japanese company is "reasonably optimistic that at the end of the day common sense is going to prevail from both sides".
Over the years, Nissan has invested around £4bn in its British manufacturing base - including a £100m boost last September.
Before the referendum, the car maker said it would sue the Vote Leave campaign for using Nissan branding in campaign materials, despite repeated requests that they stop doing so.
“Permission to use our name and logo was not requested. If it was, it would not have been granted,” Nissan said in June.