IFP leader Mangosuthu Buthelezi believes that a group of ANC members, "who hold an enormous amount of power", are behind the cancellation of the three-day social cohesion conference that was due to begin on Monday in Durban.
Buthelezi said he was due to deliver a 40-minute opening address at the conference.
He told reporters at a press conference in Durban that "apparently someone higher up in the chain of command" doesn't want to hear what he had to say.
"I have pursued social cohesion and reconciliation for several decades. I have much to say on the matter," Buthelezi said.
He revealed that some 500 participants had beenexpected to attend the conference.
Buthelezi said he had received the news of the cancellation at 22:00 on Sunday night.
"We were told, quite bizarrely, that no reasons had been advanced for the directive," he said.
The conference was also cancelled on May 29.
'My appointment was scuppered'
Buthelezi said he had noticed a "pattern of behaviour" that prohibits him from speaking at ANC government organised events.
In 1989, just before his release from prison, Nelson Mandela wrote to Buthelezi lamenting the violence between IFP and ANC supporters, according to Buthelezi.
"He asked that we meet immediately upon his release to find a way to stop the carnage. Of course I agreed, but for months after his release he avoided meeting with me," said Buthelezi.
In 1999, then-president Thabo Mbeki recognised the outstanding issue of reconciliation.
"He invited me to take up the position of Deputy President of South Africa," Buthelezi said.
Before this could be announced, ANC leaders in KwaZulu-Natal pressurised Mbeki into placing an impossible condition on the appointment, he said.
"They demanded that I first give KZN to the ANC, thus my appointment as Deputy President was scuppered," he said.
'Determined never to see old wounds healed'
He said one of those leaders was President Jacob Zuma. "The same Zuma who then became Deputy President," he said.
He said, while there were those in the ANC who believed in social cohesion, "there is another group who hold an enormous power, who are determined never to see old wounds healed", he said.
The eThekwini municipality, in a statement, apologised for any inconvenience caused to members of the panel and participants attending the conference.
"Once the new date of the conference has been confirmed, it will be communicated to members of the public and other stakeholders," the statement said.