A row has broken out between political allies of South Africa's governing African National Congress (ANC) over a financial donation said to be missing.
Union leader Willie Madisha says he passed the donation on
The 500,000 rand (£35,000) donation was made by an ANC businessman to the South African Communist Party (SACP) in 2002.
The president of the Congress of South African Trade Unions, Willie Madisha, told journalists he passed the money to Communist Party leader Blade Nzimande.
But Mr Nzimande denies ever having received the sum.
The SACP chairman, Gwede Mantashe, said a task team had been set up to examine the "two contradicting statements".
Inquiry under way
Speaking at a news conference in Johannesburg after speaking to an internal SACP inquiry into the matter, Mr Madisha said he had received the funds and passed them on to Mr Nzimande.
"I'm willing to go to the courts because I respect the laws of the land. I'm willing to go and actually prove that, yes indeed, this did happen," he said.
However, Mr Nzimande earlier denied ever having received the donation, said to have been made by a businessman.
"I wish to place it on record that I've never received the alleged 500,000 rand from any person, as is alleged.
"This is part of a concerted smear campaign primarily directed at discrediting the image and reputation of the SACP and tarnishing my image and integrity," he said.
'Bordering on hypocrisy'
Mr Madisha has been publicly criticised by the SACP - of which he is also a member of the central committee - for implicating Mr Nzimande.
Mr Madisha said such attacks were unfair, adding that the party had "already tried, judged and sentenced me in the court of public opinion" before he told his side of the story.
But the SACP chairman dismissed his claims, saying that Mr Madisha had "sat on the information" for more than five years, failing to disclose he had received the money.
"He didn't come to the structures in his own party but went public - I think that is bordering on hypocrisy," said Gwede Mantashe.
The BBC's Mpho Lakaje in Johannesburg says the ANC is quiet about the ongoing dispute.
The relationship between the ANC, SACP and Cosatu dates back to apartheid days, when the parties worked together to dismantle white minority rule.
Our correspondent says the alliance is playing a crucial role in the country's politics as the ruling party prepares to elect a successor to President Thabo Mbeki.