At an event in the swing state of Pennsylvania, Musk, the world’s richest man, with an estimated wealth of $246bn (£190bn), announced he would be giving away $1 million (£774,000) per day to registered voters in seven key states who had signed a petition for his America PAC (political action committee).

The Justice Department has sent a letter to tech billionaire Elon Musk’s super PAC, America PAC, warning that its $1 million daily giveaway in battleground states may run afoul of federal law, a source familiar with the matter said.