The ANC currently stands on 54.7% of people surveyed, down 1.3 percentage points from the December 2018 result of 56%.
The main opposition Democratic Alliance party is at 21.8%, which is a 3.1% percentage point increase from 18%.
According to the poll, conducted in February, the Economic Freedom Fighters led by Julius Malema currently stands at 12.2%. This is a 1.2 percentage point gain from 11% recorded in the December snap poll for the red-clad radical politicians.
The first poll that the IRR conducted was in September 2018, which showed that the governing party was increasing its support base.
However, the IRR said that seems to have changed as opposition parties begin to make in-roads ahead of the 8 May elections.
In the survey, the IRR said that it had interviewed 1,600 registered voters on the telephone between 12 and 26 Feb. The margin of error was 3.3 percentage points.