Japan’s foreign minister has warned against a no-deal Brexit and urged the next PM to “take good care” of the 1,000 Japanese companies operating in the UK.

Taro Kono said he had worked with both Jeremy Hunt and Boris Johnson as foreign secretary and had always said to them “please, no no-deal Brexit”.

“We are very concerned with this no-deal Brexit,” he told BBC Radio 4’s Today programme. “That would have a very negative impact on their operation.

“Right now, it’s my counterpart Jeremy Hunt and his predecessor Boris Johnson – I know them very well, I have been working with them.

“So, whoever wins and whoever becomes a new leader for the UK would consider those foreign companies operating in the UK and take good care of them.”

His warning comes as Theresa May is due to visit Japan for the G20 summit in Osaka on Friday and Saturday.

Kono said he was particularly worried about car companies relying on just-in-time supply chains, which currently have a “very smooth operation” importing and exporting to central Europe but may grind to a halt with no deal, the Press Association reports.

“If they have to go through actual customs inspections physically those operations may not be able to continue,” he said.

“Some companies already start moving their operation to other places in Europe…

“Whenever we have had meetings that was one of the major issues – please no no-deal Brexit.”

Kono said he understood the UK was interested in joining the Trans Pacific Partnership (TPP), whose members include Japan, the US and Australia.

He said: “Considering the relationship between UK and Japan we will be happy to negotiate a new trade deal, but I think you have to get out of the EU first before we can negotiate.”

He said any trade deal would not begin immediately after Brexit and there would be “some kind of gap” where the UK had to trade on World Trade Organisation (WTO) rules.

Kono said he knew both the former and the current foreign secretaries very well and revealed he had a signed copy of Johnson’s book about Winston Churchill.

He also praised Hunt’s Japanese language skills and said “he has very good knowledge about Japan and Asia” and that both men were “very good friends of mine”.