South Africa's main opposition on Sunday called for a full investigation into the government's failure to arrest Sudanese president Omar al-Bashir, who is due to face charges of genocide at the International Criminal Court.

The Democratic Alliance (DA) said it wanted the Public Protector's office to determine who was responsible for authorizing the use of state resources to enable al-Bashir’s departure.

Last Monday, before a Pretoria court ruled that the leader should be held in the country and the ICC's arrest warrant executed, Bashir flew out of the Waterkloof Air Base heading for Khartoum.

Bashir, who has controlled Sudan for over 25 years, has been indicted by the ICC for war crimes and crimes against humanity. He was in Johannesburg for an African Union summit.

South African officials did not respond to requests for comment, while President Jacob Zuma avoided questions on the subject after a Q&A session in parliament was abandoned on Thursday.

"As the days pass since Sudanese President Omar al-Bashir fled the country, a growing body of evidence points to an elaborate and well-coordinated plot by the Presidency, in collusion with the Security Cluster, to facilitate his escape," the DA statement read.

The party said it had forwarded a motion to have Bashir's departure debated in the National Assembly on Tuesday, adding that it would quiz foreign minister Maite Nkoana-Mashabane at a committee early on Tuesday.

The South African government has maintained that Bashir along with all delegates attending the AU summit were granted immunity.

The United Nations and the U.S. State Department have both expressed disappointment at South Africa's failure to detain Bashir.