President Jacob Zuma should act against public works minister Gwen Mahlangu-Nkabinde for failing to co-operate with a probe into two controversial building leases, the Public Protector recommended on Thursday.

Advocate Thuli Madonsela was releasing her report on the lease of Durban's Transnet Building.

She said Mahlangu-Nkabinde had "failed to meet the requisite stewardship as was expected of her".

Her failure to co-operate with the investigation amounted to improper conduct.

Madonsela said the police's attempts to lease the building from property tycoon Roux Shabangu amounted to maladministration.

The failure of police chief General Bheki Cele to ensure the correct tender procedures were followed with respect to the Transnet Building amounted to maladministration, she said.

The conduct of department of public works officials and senior police officials was also improper and unlawful.

Madonsela said the Durban lease would have been worth R1.16-billion over 10 years.

She said the market value of the building meant it should have been leased at R40/m² and not the R125/m² ultimately agreed on.

Referring to former director general Siviwe Dongwane's claim that he felt pressured to approve the lease, she said she could not find any evidence of this.

The police and Shabangu had denied putting pressure on him, but Madonsela said she was inclined to believe Dongwane because "towards the end of November he changed mysteriously".