Archbishop Desmond Tutu launched a blistering attack on the South African government on Wednesday for failing to use its influence in the United Nations Security Council to oust President Robert Mugabe from power.

The Nobel peace laureate's comments came after Mugabe claimed African leaders were not brave enough to ask him to step down.

Interviewed by BBC Radio 4's Today programme, Tutu said he was "deeply distressed" over South Africa's stance on the soaring humanitarian crises and political deadlock that had gripped neighbouring Zimbabwe since September.

"I certainly am ashamed of what they (South Africa) have done in the United Nations.

"It's awful to think… I was amongst those who have suggested that Mr Mugabe be given a soft landing."

Tutu said he hoped – albeit "futilely" – that the African Union could use the "threat" of force to remove Mugabe.

"He needs to be warned and his cronies must be warned that the world is not just going to sit by and do nothing, it is going to try to remove them and in addition he (Mugabe) is going to be charged before the ICC" (the International Criminal Court in The Hague).

South Africa had betrayed its legacy by allowing the Zimbabwean crises to unfold, Tutu said.