South Africa's ruling ANC is asking Winnie Mandela to clarify comments attributed to her which starkly criticise her ex-husband, Nelson.
Mrs Mandela was quoted in UK newspaper the Evening Standard as saying former President Mr Mandela was a "sell-out" who had agreed a "bad deal for blacks".
The Mandelas were leaders of the struggle against the apartheid regime of the white-minority government.
The ANC said it wanted to verify the report before commenting further.
Mrs Mandela is thought to be in the US, and her office has refused to comment on the report.
Differing speech
She apparently made the comments in an interview with the wife of Nobel Prize winning author VS Naipaul.
The newspaper reported her as saying the name Mandela was "an albatross around the necks" of her family.
She expressed disappointment that her former husband had lost some of his revolutionary spirit after 27 years in jail.
And she indicated that her daughters - both in their 50s - now had difficulty accessing their father because of red tape.
The BBC's Karen Allen, in Johannesburg, says the comments stand in stark contrast to the warm speech she made a few weeks ago commemorating the 20th anniversary of Mr Mandela's release from jail.
On that occasion she praised his "unwavering commitment to the struggle".
Mr Mandela became South Africa's first democratic president in 1994.
Source: bbc.co.uk/
