BRITAIN and Japan will work "quickly" to establish a new economic partnership after Brexit, Theresa May has insisted.

The Prime Minister said the two countries wanted to see a "swift conclusion of the ambitious EU-Japan economic partnership agreement" and that the UK would be free to sign new bilateral trade agreements in any interim period after Brexit.

A joint statement committed both nations to treat as an “immediate priority” working towards the economic partnership agreement.

Shinzo Abe, the Japanese premier, noted how new investment by Japanese companies in the UK showed the "profound trust" they had in the British economy.

Japan's corporate sector has raised concerns about the UK's decision to sever ties with Brussels and Tokyo previously made clear it wanted Britain to remain in the bloc.

Speaking at a press conference in Tokyo during her visit to Japan, Mrs May said: "Announced earlier this month, our intention is that the UK will be free to sign new bilateral trade agreements with partners around the world in any interim Brexit period, and we have agreed here today that we want to see a swift conclusion of the ambitious EU-Japan economic partnership agreement.

"Prime Minister Abe and I have agreed that as we exit the EU we will work quickly to establish a new economic partnership between Japan and the UK, based on the final terms of that agreement.

"We will set up a new joint working group to examine how we can unblock remaining barriers to trade and take steps to build the closest, freest trading relationship between the UK and Japan after Brexit."

Speaking through a translator, Mr Abe said: "The fact that, after the decision on Brexit, Japanese companies are continuing to make new investment into the United Kingdom...shows the profound trust that Japanese companies have toward the British economy.

"It is important for the world economy to realise Brexit from the EU which is smooth and successful.

"With this in mind I have asked the Prime Minister May for her continued consideration for ensuring transparency and predictability so as to minimise its impact on the business activities, including the Japanese companies."

He added: "We also agreed to have further enhancement of the dialogue between the two nations for the strengthening of the bilateral economic relations after the Brexit."

However, Alistair Carmichael, the Liberal Democrat Chief Whip, said Mrs May had gone to Japan seeking a new trade deal but instead had to admit the "biggest priority will be completing the one the EU is already negotiating" with Japan.

The former Scottish Secretary said: "Once again the promises of the Brexiteers have been dashed on the rocks of reality."

Labour’s Wes Streeting, on behalf of Open Britain, which campaigns for close ties with the EU, claimed Mrs May had suffered a “humiliating rebuff” from Mr Abe.

He said: “Theresa May’s end of summer trip to Japan has turned into a nightmare.

“She went there promising that Britain would be able to copy the EU’s emerging trade deal with Japan. She is leaving with a flea in her ear from the Japanese Prime Minister about the need for a softer Brexit to help the Japanese companies that employ thousands of Britons.”