Democratic Alliance leader Helen Zille on Friday questioned whether Minister in the Presidency Trevor Manuel's open letter to government spokesperson Jimmy Manyi labelling him a "racist" was planned to save face for the ANC in the Western Cape.

Zille said Manuel, along with the rest of President Jacob Zuma's Cabinet, had previously agreed on amendments to the Employment Equity Act which imposed national demographic quotas on the provinces.

Writing in her weekly newsletter, she questioned why Manuel did not speak up earlier.

"The fact is that Manuel endorsed Manyi's racist legislation when it mattered. Why did he not speak up then?" she asked in her weekly online newsletter.

Zille said close observers of politics knew what was behind Manuel's "sudden change of heart".

"We know that he has been tasked with repairing the ANC's image among coloured people in the Western Cape. And we know he is backing the new ANC provincial chairperson Marius Fransman.

"And so the questions remain: was Trevor Manuel's intervention a carefully co-ordinated ANC strategy of 'damage control' in the Western Cape?"

In the open letter, which was published in the Mercury newspaper, Manuel hit out at Manyi over his comments about coloured people.

"I want to draw your attention to the fact that your statements about 'an over-concentration of coloureds' are against the letter and spirit of the South African Constitution, as well as being against the values espoused by the Black Management Forum since its inception," Manuel wrote in the letter.

"I want to put it to you that these statements would make you a racist in the mould of HF Verwoerd [Hendrik Verwoerd, former South African prime minister, dubbed the 'architect of apartheid']."

Manyi, then the director general of labour, said in a show broadcast on KykNet's Robinson Regstreeks in March 2010 that there was an "over supply" of coloureds in the Western Cape.

Zille said Manyi's remarks were despicable and had no place in a democratic South Africa.

She once again called for him to step down with immediate effect.