British American Tobacco and Imperial Brands have had £8.6bn wiped off their stock market value as US regulators prepare to crack down on the sale of flavoured e-cigarettes and menthol cigarettes.

Shares in BAT, the sixth-biggest company in the FTSE 100 and maker of brands including Lucky Strike, Dunhill, Rothmans and Benson & Hedges, fell by 10.6%, sending its market value plummeting from £76bn at close on Friday to £68bn at the end of trading on Monday.