Disparate groups have paid tribute to former president Nelson Mandela a year after his death, agreeing that his contributions to securing constitutional democracy in South Africa should never be forgotten.

"This is a day to reflect on the momentous life of Comrade Tata Nelson Rolihlahla Mandela who served South Africa, and all humanity, in a way that no one individual has ever done or is ever likely to in the foreseeable future," Congress of South African Trade Unions spokesperson Patrick Craven said in a statement.

"He left it up to us and future generations to continue that struggle to see the promises of the Freedom Charter brought to life."

Former president FW de Klerk, who shared the Nobel Peace Prize with Mandela in 1993 for his role in ending apartheid, said Madiba's life represented the struggle for freedom and non-racial democracy for the majority of South Africans.

"Through his remarkable charm and magnanimity he was able to persuade his fellow leaders in the ANC and most of his former opponents and critics to join him on a peaceful march to a non-racial and democratic society," De Klerk said in a statement.

"Although Nelson Mandela is no longer physically with us his legacy remains to guide us as we continue our journey into the third decade of our new society."

Archbishop Emeritus Desmond Tutu said in a statement that Mandela taught the world to never give up hope.

"This is as valid in the context of his legacy today as it was in 1963, when he was sentenced to life imprisonment, and in 1994."

Mandela respected everyone, irrespective of class or ethnicity, Tutu said.

"Our obligation to Madiba is to continue to build the society he envisaged, to follow his example.

"A society founded on human rights, in which all can share in the rich bounty God bestowed on our country."

Technology Minister Naledi Pandor said Mandela laid the foundation for a new society, free of racial divisions and full of hope for the future.

"President Mandela understood that patterns of behaviour are not accidental products of nature, but are acquired through social interaction and nurturing."

Mandela died aged 95 on December 5 last year.