Nissan would focus efforts on its UK plant and would pull out of mainland Europe if Brexit leads to tariffs on car exports, reports suggest.
The carmaker plans to "double down" on its Sunderland base in a bid to dramatically increase its share of the UK market, according to the Financial Times.
Market share in the UK stands at 4%, but Nissan believes it could increase that to 20% - one in every five new cars sold - under the contingency plan.
Nissan would close its van-making plant in Barcelona while also shutting its facility in France.
Nissan's Sunderland plant, which produces Qashqai, the Juke and the Leaf models, employs around 6,000 people and is a major employer in the north-east of England.
A spokesman for Nissan Europe denied that the contingency plan exists.
"We’ve modelled every possible ramification of Brexit and the fact remains that our entire business both in the UK and in Europe is not sustainable in the event of WTO tariffs,” the spokesman said.
"We continue to urge UK and EU negotiators to work collaboratively towards an orderly balanced Brexit that will continue to encourage mutually beneficial trade."
The report came as Boris Johnson prepares to unveil a tough negotiation strategy ahead of trade talks with the EU.
In a speech today (Monday), the Prime Minister will say there is "no need" for the UK to sign up to Brussels regulations in exchange for a tariff-free agreement.