South African police are investigating President Jacob Zuma over a £14.5m taxpayer-funded refurbishment at his rural homestead, according to parliamentary papers.

In a written response to MPs published on Monday, police confirmed that an investigation had been launched into spending at the property.

Zuma, who was re-elected in May, has said he had no knowledge of the work, including the construction of a swimming pool, private clinic and amphitheatre. His government says all the refurbishments at the homestead in Nkandla, in the south-eastern province of KwaZulu-Natal were security related.

The issue has become a lightning rod for criticism of Zuma’s administration, which is seen by many South Africans as tolerant of corruption and incompetence.

The opposition leader Mmusi Maimane, of the Democratic Alliance, laid the corruption charges against Zuma in March after the public ombudsman, Thuli Madonsela, ruled that Zuma had “benefited unduly” from the construction and ordered him to pay part of the cost.

At the time, Maimane said: “There can be no doubt that this Nkandla palace was built on corruption by the president for the president with our money.” He and other opposition politicians have repeatedly called for Zuma to resign.

In a written statement to parliament, the police minister, Nathi Nhleko, said: “The investigation in this regard has been initiated and no further information can be disclosed at this juncture as the matter is still sub judice. Suffice to say that all processes have been followed.”

When Zuma appeared before parliament in August, opposition parties repeatedly chanted “pay back the money” until riot police were called in. Zuma has not returned to parliament since, provoking even more criticism from MPs, who last week demanded to know when the president would reappear.

The deputy president, Cyril Ramaphosa, responded to the calls by saying: “For as long as the type of behaviour that one is getting from members of the parties in opposition persists, we will not have a good relationship between parliament and the executive.”