Outspoken Tesla CEO Elon Musk has taken a series of swipes at Apple in an interview with German newspaper Handelsblatt, referring to the Cupertino-based company as “Tesla’s graveyard.”

When questioned over claims that Apple has been poaching key members of Tesla’s staff to work on its rumored self-driving car project, Musk said: “Important engineers? They have hired people we’ve fired. We always jokingly call Apple the ‘Tesla Graveyard.’ If you don’t make it at Tesla, you go work at Apple. I’m not kidding.”

Musk continued his taunts against Apple when asked if he saw the company as a potentially serious competitor in the electric car market. “Did you ever take a look at the Apple Watch?” was his jokey response. He added: “No, seriously: it’s good that Apple is moving and investing in this direction. But cars are very complex compared to phones or smartwatches. You can’t just go to a supplier like Foxconn and say: ‘Build me a car.’ But for Apple, the car is the next logical thing to finally offer a significant innovation. A new pencil or a bigger iPad alone were not relevant enough.”

In 2014, Musk confirmed that Tesla and Apple had taken part in possible acquisition talks, but it ultimately led to nothing. When asked at the time if the electric vehicle company was for sale, Musk said it was “unlikely.”

Apple - which was named the world's most valuable brand for the third year running earlier this week - is said to be speeding up development of ‘Project Titan,’ its self-driving car initiative. Apple executives were reported to have met with California’s department of motor vehicles last month to discuss plans for an “autonomous vehicle.”

Tesla revealed its $132,000 Tesla Model X last week, although a lot of the attention was focused on the SUVs ‘bio-weapon defense mode.' The vehicle’s unveiling came nearly two years later than scheduled; Musk admitted that the "difficulty in engineering" some of the SUV's parts had been greater than he had originally expected.