The number of South Africans living on less than $1 a day has more than doubled in a decade since shortly after the end of apartheid.
There are more losers in post-apartheid South Africa
The South African Institute of Race Relations survey said 4.2m people were living on $1 a day in 2005.
This is up from 1.9m in 1996, two years after the first all-race elections.
"Poverty has increased both in absolute numbers and proportionally," SAIRR said in a statement, blaming the rise on unemployment and HIV/Aids.
Despite good economic growth in recent years, unemployment has remained consistently high at about 26%.
SAIRR says poverty is also increasing among the white population while inequality was growing among the black population.
The government plan to halve poverty and unemployment by 2014 was ambitious, said SAIRR.
"It is going to take a long time to get rid of the poverty," said researcher Marius Roodt.
Poverty and jobs
The governing African National Congress chooses a possible successor to President Thabo Mbeki in December, with trade unions backing the former deputy president Jacob Zuma.
South Africa has failed to create enough jobs
He has criticised Mr Mbeki's government for not doing more to reduce poverty.
A government-backed report on unemployment released last month warned that a reliance on growth alone will not achieve the target of halving joblessness by 2014.
It also concluded that even if the government did meet this target, it would not go very far to relieving poverty.
The most likely areas of job growth are in domestic service, restaurants and the informal sector - none of which are well paid.
As the author of the Accelerated & Shared Growth Initiative for SA report, Miriam Altman, put it: "Poverty is something that we are likely to see in South Africa for many generations."