Mr Gray leaves his position as Head of General Expenditure Policy at Her Majesty’s Treasury to join the communications team at Downing Street.
He will replace Steve Field, who has been appointed the UK’s next Executive Director to the International Monetary Fund.
Mr Gray will take up his post after the Autumn Statement.
Notes for editors
Jean-Christophe Gray, aged 36, is currently HM Treasury’s Head of General Expenditure. He has previously held a range of posts in the department, including private secretary to the Chancellor of the Exchequer and Head of Press.