Japanese Prime Minister Shinzo Abe has cautioned Britain that a vote to leave the European Union in June's referendum on membership would make Britain less attractive for Japanese investors.
His intervention comes less than two weeks since US President Barack Obama bluntly warned Britain that it would be "in the back of the queue" for a trade deal with the United States if it dropped out of the EU.
"Japan very clearly would prefer Britain to remain within the EU," Abe told reporters during a visit to London on Thursday.
"Many Japanese companies set up their operations in the UK precisely because the UK is a gateway to the EU."
"A vote to leave would make the UK less attractive as a destination for Japanese investment."
Speaking through a translator at a news conference with Prime Minister David Cameron, Abe said about 1000 Japanese companies operate in the UK employing 140,000 people.
But supporters of a British exit from the 28-nation bloc poured cold water on Abe's comments saying Japanese companies such as Toyota, Nissan and Hitachi were committed to investing in the United Kingdom regardless of the outcome.
"Japan wouldn't accept the huge loss of control Britain has suffered because of our EU membership, so much of the public will be sceptical of the Japanese prime minister's 'do as I say, not as we do attitude,'" said Matthew Elliott, Chief Executive of the Vote Leave campaign.
Cameron, who is leading the campaign to keep the UK in the EU, said Britain benefited more from Japanese investment than from any other country apart from the US. He said Japan had investments worth a total of STG38 billion ($A73.9 billion) in Britain.
