The struggle veteran, in a letter addressed to party spokesman Jackson Mthembu, blasted the ANC, saying: "We [the Mandela family] only matter when we have to be used for some agenda."

A clearly hurt and livid Madikizela-Mandela wrote the letter in response to a request by Mthembu for a meeting to discuss the ANC's centenary celebrations, which involve former president Nelson Mandela during his birthday month.

The meeting, scheduled for July5, was also intended to deal with her travel to Limpopo, where President Jacob Zuma delivered a lecture honouring Mandela.

But Madikizela-Mandela snubbed the invitation to the event, held last night.

Instead, Ndileka Mandela, the granddaughter of Mandela from his first marriage, delivered a message from Mandela. His wife, Graça Machel, also attended, but not Madikizela-Mandela's daughters by Mandela.

Madikizela-Mandela's missive is likely to result in strained relations between her and the party that she has served for many decades.

In the letter, addressed to "Comrade Jackson", Madikizela-Mandela kicks off with an accusation of "shabby treatment" of many years, singling out the ANC's centenary celebrations in Mangaung in January.

"We are deeply hurt as the family. We did not even have a table and the situation was saved by Mrs Bridgette Radebe [wife of justice minister Jeff Radebe]."

Madikizela-Mandela complained that she had been sidelined during the preparations for the centenary celebrations. In 2011, she said, she was reduced to being merely "a spectator throughout".

She expresses her surprise at the invitation to participate.

"I was not deployed anywhere. I am the one person who has first [-hand] information about the leaders you are celebrating. I would have given you the song that was composed for that day," she writes.

Madikizela-Mandela then focuses on what she clearly considers to be deeply disrespectful treatment of her by the ANC of Mandela.

She said that in the past the ANC had no interest in celebrating Mandela's birthday except to "gate-crush [sic] family arrangements".

She takes issue with the way in which the party, through chairman Baleka Mbete, took the ANC's centenary flame to Mandela in his village of Qunu, in Eastern Cape, in May.

"The manner in which the flame was brought to Tata [Mandela] left much to be desired. There was no parade of the soldiers as there was to me. It was clear that it was done to someone's ego not to the family," the letter reads.

Madikizela-Mandela accused the party of allowing the torch to be taken to her Soweto home only after intervention by Gauteng ANC leaders, including provincial chairman Paul Mashatile and provincial secretary David Makhura.

Then, in the unprecedented letter, Madikizela-Mandela turns the focus on herself, lambasting the party for neglecting her.

Though she had been in hospital several times since January 25, she had not received "even one phone call from Luthuli House" - the party's headquarters.

Clearly hurt, Madikizela-Mandela accuses Mthembu of giving a false interview, saying: "I was recuperating from an ankle operation when you did not even care what kind of an operation I had ..."

Then, effectively accusing the spokesman of lying to the public, Madikizela-Mandela writes: "I never had an ankle operation; I had a knee operation."

And, she says, the insults she mentions in her letter are merely a few of "a hundred others".

"No one has cared to establish how we are doing as a family. It is quite clear that we do not matter at all.

"We only do [matter] when we have to be used for some agenda."

Last night Mthembu said the ANC would not respond to the letter.

Madikizela-Mandela has, particularly since the unbanning of the ANC in 1990, been regarded as a contentious figure in South African politics.

Her formal political life - she was a deputy minister in South Africa's first democratic cabinet - caused considerable embarrassment to Mandela, to the point that she was removed.

Madikizela-Mandela's relationship with former president Thabo Mbeki started off relatively well and she campaigned for him to be elected president of the ANC.

But, during his term of office, relations soured and he publicly rebuffed her at a June 16 rally in Soweto in 2001.

She appears to have had a similar relationship with Zuma, supporting him after his election as party president in Polokwane in 2007.

But she became embroiled in Zuma's stand-off, and increasingly hostile relationship, with expelled ANC Youth League president Julius Malema.