"There is a big difference between freedom of speech and freedom to insult," he told a National Union of Mineworkers' congress in Ekurhuleni, in reference to a painting depicting President Jacob Zuma with his genitals exposed.

"It is not you who are insulting us who must tell us how we must feel, but it is us who know how we feel. We have been insulted, our dignity has been assaulted and violated, and we have been made to feel naked," Nzimande said.

The portrait indicated that some South Africans had not accepted the building of a socially cohesive, non-racial country.

"We must... make it absolutely clear that the body of the president is not for sale."

Nzimande called for a boycott of City Press newspaper, which published the picture on its website.

"We must from now onwards not buy this newspaper... until it withdraws this portrait from its pages and website and issues an apology to the nation."

Calling the portrait "deeply offensive", Nzimande said it was one of the most serious violations of the black body in recent times.

It was part of a tradition of racist thinking in South Africa.

"This portrait is the same as what was done to Sarah Baartman," he said, referring to the Khoisan woman who was displayed as a freak in 19th Century Europe.

Nzimande also spoke out against corruption and self-enrichment in the revolutionary movement, calling it the "new tendency".

This trend was found not only in the ANC, but across all revolutionary organisations, including trade unions.

"It is wrong to think that the only place where leaders can be corrupted or co-opted is in the ANC or government," he said.

Leadership positions were used to access either union funds and business, or to enter into business generally.

Employers even paid individuals within the NUM to turn it into a "sweetheart" union, he said.

"Those who seek to buy members in our organisations, will tomorrow also sell our organisations and ultimately our country to the highest imperialist bidder."

Global capitalism was facing one of its most severe crises since the 1929 depression, he said.

It had no strategy to resolve its own crises, but punished workers and the middle class with austerity measures, and cut back social services.

This crisis was reinforcing socio-economic challenges in South Africa, including poverty, inequality and structural unemployment.

However, important policy breakthroughs had been made since the ANC's Polokwane conference.

These included the development of an overarching industrial policy, a more active role for the state in economic development and a commitment to a more radical redistribution of land.

The SACP supported moves for the creation of a state-owned mining company and a proposed mining rents regime, which would include a windfall tax.

It was also in favour of companies winning major infrastructure projects not using labour brokers, but training their workers.

Health and education were also prioritised.

The SACP was calling for the increased socialisation of the finance sector. Workers should have an effective say over the investments of their pension and provident funds.

The public works department and municipalities should have the capacity to construct social infrastructure, limiting tenders, he said.