London - In a break with the past, the youthful leader of Britain's main opposition Conservative Party on Sunday renounced Margaret Thatcher's sympathetic stance on apartheid-era South Africa.

Resisting international sanctions on the apartheid regime was a highly controversial part of Thatcher's foreign policy when she was Conservative prime minister from 1979 to 1991.

She famously branded Nelson Mandela's African National Congress (ANC) as "terrorists".

Writing in the Observer newspaper, the Tories' current leader David Cameron - who met Mandela on Wednesday during a visit to Johannesburg - declared that Thatcher was wrong.

"The mistakes my party made in the past with respect to relations with the ANC and sanctions on South Africa make it all the more important to listen now," he wrote.

"The fact that there is so much to celebrate in the new South Africa is not in spite of Mandela and the ANC, it is because of them - and we Conservatives should say so clearly today."

Cameron, 39, who has been shifting the Conservatives' policies to the centre since becoming leader since December last year, went on to describe Mandela, 88, as "one of the greatest men alive".

There was no comment from Thatcher, 80, who suffers from memory loss and makes few public appearances, but remains a revered figure among older Conservative supporters. - Sapa-AFP