HONDA is one of the Japanese automakers most likely to close UK plants after a ‘hard Brexit’ in order to avoid rising assembly costs, according to reports.

The price of making a vehicle without frictionless trade with the EU could climb by £2,372 ($3,337) under estimates provided by London-based PA Consulting.

Honda, which has a plant in South Marston, was identified as one of the Japanese-owned firms most likely to leave their plants in the event of Hard Brexit.

A separate report by Bloomberg gave a stark picture of the road ahead for the British car industry, with a split potentially being “a prelude to wholesale shutdowns”.

The latest warnings follow the Japanese ambassador raising the prospect of the island’s top companies leaving Britain if no free trade deal is struck.

Koji Tsuruoka spoke earlier this month after Honda and other Japanese-owned business met with the Prime Minister and Cabinet members at Downing Street.

Both Swindon MPs responded by saying Honda remained committed to Swindon and had a close relationship with the British government.

However South West MEP Molly Scott Cato, who toured the Swindon plant last month, believes the future is far from secure.

She said: “An awful lot of people are engaging in a lot of wishful thinking because they are being encouraged to do so by the government. We have ministers and the local MPs engaging in the same kind of wishful thinking and it’s watering down the level of concern there would otherwise be.

“The Japanese are an extremely mild-mannered and polite people. You don’t have the Japanese ambassador plus the captains of his industry in Britain, who are responsible for 140,000 jobs plus several times that in the supply chain, turning up in Downing Street unless they are very worried indeed. What is great about the Japanese is that they have been totally honest from day one. It was about two weeks after the referendum that they said, ‘we like Britain, we like working here, we’ve invested massively here, but if you leave the customs union and single market it’s not going to be the same situation as before’.

“Now we have got to this crunch period where the government has to decide on whether we stay in the single market and customs union and they [the Japanese] are saying very clearly they can’t maintain the same level of commitment if we’re not in those two arrangements.”

Ms Cato, met associates and drove a hydrogen car at the manufacturing plant after the tour was organised by Patrick Keating, Honda's European Government Affairs Manager.

But she doesn’t believe that Honda has provided firm assurances that it will continue investing in its South Marston plant no matter what deal is struck with the EU.

The Green MEP said: “The margins in the car industry are very tight, they are saying that if they face any friction they will no longer consider it to be profitable to manufacture cars in Swindon.

“No one is saying they are going to close their plant on March 29, 2019, because they have a massive sunk investment there. What they are going to do is, the next time they make a decision they are going to find it’s more profitable somewhere where they don’t have to go through all the customs requirements to move their components. That was obvious from the start but we have Brexiteers who are putting ideology ahead of what’s really important for the economy. They will say there are bumps in the road. It’s not bumps for them, it’s bumps for the people who work at Honda.

“That’s what’s so irresponsible about the way the government is behaving.”

A spokesman for Honda said: “Honda is committed to its UK and European operations and continues to engage with government to ensure the best business conditions after the UK exits the EU.”

Both Swindon’s Conservative MPs dismissed fears of the automobile giant pulling out of the borough when they spoke to the Adver earlier this month.

South Swindon MP Robert Buckland said: “The government is working closely with Honda and other car manufacturers to ensure that their Brexit concerns are met, for example the supplying of components.

“Honda has invested a huge amount in the Swindon plant and I believe we are in a strong position when it comes to future models and further expansion.”