Japanese officials want "an uninterrupted and transparent" Brexit process as exporters highlight concerns over their presence in the U.K. and future access to the EU's single market.
In a memo prepared by the Japanese government and business task force, and seen by CNBC, Japan asked British and European officials to ensure "predictability" during the divorce process and thus offset any economic impact for Japanese businesses.
"Uncertainty is a major concern for an economy. We hope that predictability is secured whereby all stakeholders, not just the negotiating parties, have a clear idea of the post-Brexit landscape," the memo said.
"This will be possible if the Brexit negotiations are conducted through an uninterrupted and transparent process, which could include arrangements such as the establishment of a provisional period and, if there need to be institutional changes, the granting of time for the transition and publicizing of such changes," the document read.
Many Japanese firms, from banks to automakers, have established production bases in the UK taking advantage of tariff-free trade with the rest of Europe. According to Nikko Asset Management, 2015 saw a 10-year high for total auto production in the U.K. from Japanese firms – 1.58 million cars were produced, of which 57.5 percent were sold in the EU's single market.
"Overall, the feeling in government circles in Japan is one of betrayal, and in the corporate sector one of disbelief," Karel Lannoo, chief executive officer at the Centre for European Policy Studies, told CNBC on Friday.
Lannoo, who spoke with Japanese officials last week, added: "The U.K. was sold as a gateway to the EU, which is now gone. The corporate sector is busily exploring other location possibilities, of which we have read in the media."
Some of the biggest Japanese firms in the U.K. market include: Fujitsu, Toyota, Nissan and Honda. Nissan decided to give the greenlight to new production in the U.K., despite concerns over Brexit, because it could not postpone the decision.
"We had to make a decision on investment now," Carlos Ghosn, chairman and chief executive officer of Renault-Nissan Alliance told CNBC earlier this month, adding that the British government gave "reassurances" that the firms competitiveness would not be undermined.