The SA Institute of Race Relations (SAIRR) found that the number of domestic workers had fallen from 1 215 000 in 2003 to 1 153 000 in 2012.

This was a five percent decrease.

SAIRR researcher Georgina Alexander said the decrease was significant because the country's middle class had increased over the same period.

Average household income had also risen by 113% over the last decade.

"The inference is that South Africa's middle classes are less inclined to employ domestic workers than was the case in past decades," Alexander said.

"The reasons for this are unknown and have to be left to speculation."

She said stricter labour laws and minimum wage regulations, security concerns, smaller homes and properties, and racial and cultural shifts in middle class attitudes, could have contributed to the decline.

Increased prices for electricity, rates, and fuel, and higher household debt levels, could also have played a role.