It is like a woman inviting a man whom she knows is HIV-positive to come to bed with her

Winnie Madikizela-Mandela

The predecessor of the NNP, the National Party, created and operated apartheid from the late 1940s until it began dismantling the system in 1990.

After all-race elections swept the ANC to power in 1994, it participated in a national unity government, until pulling out in 1996.

The two parties said in a joint statement: "The ANC and the NNP will cooperate in all areas of South Africa's political life."

"The spirit of participatory governance will also be reflected in appointments in national government, parliamentary and other appropriate structures," the statement said.

They also said they would rule the Western Cape province in an equally divided coalition.

Opposition

Earlier this month, the NNP withdrew from the official opposition, the Democratic Alliance, and began talks with the ANC.

A row over street names changed South African politics

Its withdrawal was prompted by a farcical scandal over plans by the then NNP mayor of Cape Town, Peter Marais, to rename two city streets after leaders of the fight against apartheid.

Mr Marais was forced out of office for allegedly misleading the public over his plans.

It was the ensuing crisis caused that prompted the NNP to move towards the ANC.

Legislation is also due before parliament to allow legislators to switch their party affiliations.

Analysts say these developments combined with the latest power-sharing pact could trigger the first major political realignment in South Africa since the end of apartheid.

One-party fears

But critics have expressed fears the deal could make South Africa effectively a one-party state given the massive majority won by the ANC of President Thabo Mbeki in general elections in 1999.

NNP leader Marthinus van Schalkwyk has in the past been at pains to point out that the NNP was interested not in a merger, but in "co-operative government".

ANC leader Thabo Mbeki: Western Cape within his sights

Unimpressed by such assertions, Nelson Mandela's former wife sharply criticised the negotiations.

"It is like a woman inviting a man whom she knows is HIV-positive to come to bed with her," she told a South African radio station.

During the apartheid era, the then National Party outlawed the ANC as a terrorist organisation and imprisoned Nelson Mandela and other ANC leaders.

South Africa's press has speculated that Mr van Schalkwyk could be on the brink of a cabinet post.

But Mr Van Schalkwyk declined to comment on any appointment.

"It is the president's prerogative to appoint people to his cabinet, but there is a commitment to co-government at all levels," he told the Reuters news agency.

Stinging attack

In a speech to a rally in Cape Town on Sunday, Mr van Schalkwyk launched a stinging attack on his former ally, Democratic Alliance leader Tony Leon.

DP leader Tony Leon: Called on the NNP's Cape Town mayor to resign

He said the the Democratic Party - which was the majority party in the Democratic Alliance - was only interested in improving the lives of an elite few.

He went as far as to compare Mr Leon with the late Andries Treurnicht, the leader of the right-wing white Conservative Party in the 1980s and early 1990s during apartheid.

Mr Leon has in turn accused Mr Van Schalkwyk of undermining efforts to form a strong democratic opposition.

The DP has traditionally drawn much of its support from the English-speaking white community. The NNP has had strong support in the Afrikaner community and among Cape Town's one million strong coloured community.