South Africa's parliament is expected to abolish the country's independent crime-fighting unit, the Scorpions.
The body has been behind several high-profile investigations of political figures, including a corruption probe against ruling party leader Jacob Zuma.
Last month a judge dismissed charges against Mr Zuma, who is expected to become president after polls next year.
Opposition parties accuse the governing African National Congress of waging a political campaign against the unit.
The BBC's Mpho Lakaje in Johannesburg says Thursday's parliamentary debate and vote are seen as formalities, as the ANC had already spelled out plans to disband the Scorpions.
It follows a series of failed attempts by opposition parties and members of the public to save the body.
Legislation supported by the ANC will create a new force of criminal investigators that will be integrated into the police.
The Scorpions unit has shaken South Africa's political landscape in the last few years, probing and arresting several prominent politicians, our correspondent says.
Among those pursued were ANC former chief whip Tony Yengeni and Winnie Madikizela-Mandela, the former wife of ex-President Nelson Mandela.
The Scorpions also led an investigation against suspended police commissioner Jacki Selebi, who faces trial next year.
But observers say the unit, formally known as the Directorate of Special Operations, pushed its luck too far when it pressed corruption charges Mr Zuma.
That case was at the centre of a power struggle between Mr Zuma and Thabo Mbeki, with Mr Zuma's allies accusing Mr Mbeki's supporters of using the Scorpions to stop his rival gaining power.
Mr Mbeki stepped down as president after Judge Chris Nicholson suggested that he had interfered in the case against Mr Zuma.
The former president has strongly denied this and has appealed against the judge's ruling.