The former South African president Jacob Zuma has refused to testify before a major corruption inquiry, claiming he was being questioned unfairly.

Zuma was scheduled to give evidence throughout the week. But when the court reconvened on Friday morning after a 48-hour adjournment at his request, the 77-year-old’s politician’s lawyer, Muzi Sikhakhane, said he would take no further part in proceedings.

Sikhakhane said Zuma had been subjected to “relentless cross-examination” in a process that had become “political”.

Late on Friday his legal team said a compromise had been reached and the former president had agreed to submit statements to the inquiry in response to specific questions.

The inquiry is mandated to investigate allegations of “state capture” in South Africa during Zuma’s presidency, which ended last year when he was ousted amid graft allegations.

It was set up after an ombudsman’s report uncovered apparent evidence of improper contact between three wealthy businessmen brothers, Atul, Ajay and Rajesh Gupta, and senior officials in Zuma’s administration.

The report, which stopped short of asserting criminal behaviour had taken place, called for an investigation into whether Zuma, some of his cabinet members and some state companies had acted improperly.

In testimony on Monday, Zuma said he had been smeared and that he was the victim of a conspiracy organised by foreign intelligence agencies. On Tuesday, he appeared increasingly uncomfortable as he was questioned by Raymond Zondo, the senior judge who chairs the inquiry.

There were concerns Zuma might use the hearings as a platform to attack his successor, Cyril Ramaphosa, who led the ruling African National Congress (ANC) to a convincing election victory in May but has so far been unable to fully assert his authority over the party. But such fears have so far proved unfounded.

The ANC is deeply divided between factions loyal to Zuma and reformists who support Ramaphosa.

Zuma appointed loyalists to hundreds of top positions in the police, tax revenue service, intelligence agencies and other public bodies.

Ramaphosa, a labour activist and tycoon who served as Zuma’s vice-president, faces attacks from another state anti-graft agency over donations he received for his campaign to lead the ANC in 2017.

Busisiwe Mkhwebane, an ombudsman constitutionally charged to investigate allegations of wrongdoing by state officials, told reporters on Friday that Ramaphosa had “deliberately misled” parliament about a 500,000 rand (£28,700) donation and violated the constitution.

Questioned by opposition politicians, Ramaphosa first said the donation had been a consultancy fee paid to his son Andile by a company implicated in corruption of government officials. The president revised his answer in November to say that the money had in fact been a donation to his campaign fund.

Mkhwebane accepted that the mistake had been made “in good faith” but said the president should “have allowed himself sufficient time to research … a well-informed response”. This amounted to deliberate deception and was thus unethical and unconstitutional, she said, a charge that Ramaphosa’s allies said was contradictory and would be challenged in court.

Ramaphosa has repeatedly said he would be prepared to appear before the commission.

The charge against the president will undermine his efforts to purge the ANC of Zuma’s supporters and distract attention from the Zondo inquiry.

The ombudsman, known as the public protector, is appointed by the president on the recommendation of a parliamentary panel.

This year, Mkhwebane’s report into a scandal involving huge government grants to a dairy farm was declared invalid by a court because of investigative shortcomings, particularly a failure to examine the role of senior ANC officials close to Zuma.

Mkhwebane has also claimed that the public enterprises minister, Pravin Gordhan, a close ally of Ramaphosa, abused his powers during a stint as finance minister. Gordhan has denied the charge, which is seen as an indirect attack on the president.

The mutual accusations of graft have underlined the depth of divisions within the ANC and will further disillusion voters. A quarter of a century after the end of the apartheid system, South Africa remains one of the most unequal societies in the world, with soaring unemployment, a flagging economy and high levels of violent crime.

On Thursday troops were deployed in poor neighbourhoods close to the western city of Cape Town after a spate of gang-related killings. Earlier this year South Africans endured rolling electricity cuts.

Zuma faces a separate corruption investigation involving 16 charges of fraud, racketeering and money laundering relating to a deal to buy European military hardware to upgrade South Africa’s armed forces in 1994. He denies the charges.