The slogan "Kill the farmer, kill the Boer" used by some black nationalists during the fight to overthrow apartheid has been classified as hate speech by the South African Human Rights Commission.
"We have concluded that the calling for the killing of a
group of people is an advocacy of hatred, which must amount to harm," the South African Press Association quoted Commissioner Karthy Govender saying.
However, the ruling by the commission is only a recommendation and does not oblige the judiciary to follow it.
It followed an appeal against an earlier ruling that the slogan was merely distasteful but not illegal.
Thursday's ruling could open the way for claims of damages against people using the slogan in the future.
A number of white South African farmers - who own most of the country's best land - have been murdered recently in attacks described as being racially-motivated.
The word Boer means farmer and is often used to refer to South Africa's Afrikaaners.
'Double standards'
The white farmers have been worried by reports that the slogan had been used by members of the ruling African National Congress (ANC) at two public meetings last year.
The ANC has denied the reports.
Freedom Front leader Pieter Mulder said the ruling would end the double standards in the country that punished racial slurs against blacks, but not
against whites.
Since the end of apartheid the government has been advocating a message of racial unity.