Donald Trump has lashed out at Elon Musk after the billionaire unveiled plans to launch a new US political party, calling him a “train wreck” in an escalation of the feud between the US president and his former ally.

US President Donald Trump has hit out at former close ally Elon Musk over the multi-billionaire's plan to launch a new political party. "I am saddened to watch Elon Musk go completely 'off the rails,' essentially becoming a train wreck over the past five weeks,