South African President Cyril Ramaphosa has announced a judicial inquiry into allegations of political interference in the prosecution of apartheid-era crimes.

The announcement comes three decades after the end of white-minority rule – and after a group of survivors and victims’ relatives sued Ramaphosa’s government over a perceived lack of justice.

The Truth and Reconciliation Commission (TRC), set up in 1996, uncovered apartheid-era atrocities like murder and torture, but few of these cases progressed to trial.

Announcing the new inquiry, a presidential statement said Ramaphosa is “determined that the true facts be established and the matter brought to finality”.

The investigation is the outcome of settlement discussions in a high court case brought by 25 families and survivors.

The group, which is suing the government for damages worth $9m (£6.8m), says apartheid-era crimes were never properly investigated by the governments that came after the racist system.

Plaintiffs include the son of Fort Calata who, among a group of anti-apartheid activists who came to be known as the Cradock Four, was burnt and killed by security forces in 1985.

Their murder of the four men sparked outrage across the country and six former police officers eventually confessed their involvement to the TRC. They were denied amnesty by the commission, but were never taken to court. All six officers have since died.

For years, critics have alleged that the post-apartheid leadership of the African National Congress (ANC) formed a secret deal with the former white-minority government in order to prevent prosecutions. The ANC has denied this.

On Wednesday, the presidency acknowledged that “allegations of improper influence in delaying or hindering the investigation and prosecution of apartheid-era crimes have persisted from previous administrations”.

The head of the inquiry, along with its timetable, will soon be announced.