Panasonic's chief executive has admitted to having concerns about Tesla founder Elon Musk's erratic behaviour amid talks between the firms to increase battery production.

Musk's behavior, which included smoking marijuana on a live podcast hosted by the comedian Joe Rogan, has worried investors and led to questions over his suitability as a leader.

The freewheeling Tesla founder was recently fined by the US Securities and Exchange Commission for misleading the market in a tweet that suggested he had "funding secured" to take Tesla private.

Musk has also faced criticism for being embroiled in a public war of words with a British caver who was involved in this summer’s rescue effort of a group of trapped boys in Thailand, accusing him of being a paedophile in an extraordinary and baseless attack.

"Though Elon's comments are unpredictable, we will continue to monitor Tesla's operations to ensure no chaos there and will work in step with the company," said Kazuhiro Tsuga.

Mr Tsuga however admitted that Tesla's business has been unaffected despite the controversy.

Panasonic is the battery cell supplier for Tesla, and is currently talks with Musk to boost capacity at Tesla's Nevada Gigafactory.

When asked about any plans to invest in Tesla's plant in China, Mr Tsuga said the firm "will put priority on building additional capacity at the Gigafactory over China".