The British singer, 30, was spotted walking down Whitehall Lane in the middle of London. She was dressed casually and carried a blue horn, reported Femalefirst.
Cameron is under fire after the recently released Panama Papers revealed that he owned shares in his late father's offshore fund, Blairmore Holdings.
Although offshore accounts are typically used in order to avoid paying taxes on large amounts of money, Cameron has claimed that he sold his shares in the offshore account once he became prime minister in 2010.