The Transvaal Agricultural Union has asked the Human Rights Commission to investigate a hate speech charge against Deputy President Kgalema Motlanthe.

The charge stemmed from allegations Motlanthe had stated many farm attacks were the result of workers not being paid, and who were arrested after farmers reported them to the police prior to being paid, the union's president Ben Marais said in a statement on Tuesday.

"The deputy president's statement... creates a climate for increased attacks on farmers, their families and their employees. The database available [to Tausa] indicates that attackers are seldom known to the victims and that the latter are being attacked by unknown strangers."

Motlanthe reportedly said last week: "Some of the most brutal farm murders are committed by foreign nationals, who were brutally exploited and made to toil without any remuneration. The day when they demand remuneration, they are reported (by farmers) to the law enforcement units and are duly arrested and are sent back to their countries of origin.

"Of course, they come back and... commit the most horrendous murders. This is why we need to condemn those who take advantage of foreign nationals in this fashion."

Marais this statement could incite further violence in retribution for perceived maltreatment of employees. It advocated hatred of a specific racial and economic group and constituted incitement to do harm.