The MDA survey, its first since the election’s first round, showed Ms Rousseff with 45.5% of voter support versus 44.5% for Mr Neves. Excluding undecided voters, spoiled and blank survey responses, Ms Rousseff had 50.5% against 49.5% for Mr Neves, a senator and former state governor.

Brazil’s currency and stock markets extended losses after the poll showed Mr Neves, an investor favourite from the centrist Brazilian Social Democracy Party, losing momentum.