Cape Town - President Thabo Mbeki is failing to lead the country by keeping silent on the scandal engulfing the office of the deputy president, Jacob Zuma, Democratic Alliance leader Tony Leon said in his weekly newsletter on Thursday.

Leon said there was a prima facie case of failure against Mbeki.

"Based on the prima facie evidence before the South African public, the President has failed, and failed badly," Leon said.

"He bears direct responsibility for the corruption in the arms deal - not just as head of the government, the ruling party, and the nation, but as someone who was intimately involved in the decisions on procurement."

Leon accused Mbeki of trying to suppress any investigation into corruption in the arms deal.

"If anything, the President has struggled vigorously against attempts to expose corruption in the arms deal."

He said evidence showed that instead of assisting investigations into corruption, the Presidency has been obstructing and confounding them.

Mbeki has taken any allegations of corruption in the arms deal as being cooked up by critics of the government.

Leon said the president remained silent as the crisis surrounding Zuma unfolded this week.

"There has been a gaping hole in the leadership of our country for several days."

He said Mbeki seemed incapable of distinguishing between the national interest and party interests.

The people of South Africa would find the president guilty unless he provided a satisfactory answer to the "prima facie evidence of his failure.

"Only one answer will suffice: the President must break his silence, act swiftly and demand that the Deputy President step down."

With acknowledgements to Sapa and News24.