Julius Malema sends a BBC journalist out of a press conference Reuters

A firebrand South African youth leader today threw a BBC journalist out of a press conference, accusing him of "white tendency" and calling him a "bastard", "bloody agent" and "small boy".

Julius Malema, president of the youth wing of the African National Congress, exploded in rage when Jonah Fisher, a white Briton, interrupted him at the ANC's headquarters in Johannesburg.

The row began when Malema, who has just returned from Zimbabwe, praised Robert Mugabe's Zanu-PF party and poured scorn on the "Mickey Mouse" opposition. He mocked exiles linked to the Movement for Democratic Change, led by Zimbabwe's prime minister, Morgan Tsvangirai, for using offices in Sandton, a wealthy suburb of Johannesburg.

"They can insult us here from air conditioned offices of Sandton," Malema told journalists at Luthuli House. "We are unshaken. They must stop shouting at us. They must go and fight for their battle in Zimbabwe and win … why are they speaking in Sandton and not Mashonaland or Matabeleland?"

As Malema went on, Fisher interjected: "You live in Sandton."

Evidently stung, Malema replied: "Let me tell you, this is a building of a revolutionary party and you know nothing about the revolution."

Fisher pressed: "So they're not welcome in Sandton but you are?"

Malema snapped: "Here you behave or else you jump."

This prompted laughter from Fisher and others.

"Don't laugh," Malema growled.

Fisher commented that the situation had become a "joke".

Malema then erupted, asking for a security guard to eject Fisher and telling him: "If you're not going to behave, you're [sic] going to call security to take you out. This is not a newsroom, this is a revolutionary house and you don't come here with that tendency.

"Don't come here with that white tendency. Not here. You can do it somewhere else. Not here. If you've got a tendency of undermining blacks, even where you work, you are in the wrong place. Here you are in the wrong place."

Fisher responded: "That's rubbish. That's absolute rubbish."

Malema continued: "You can go out. Rubbish is what you have covered in that trouser. That is rubbish. You are a small boy, you can't do anything."

Collecting his dictaphone and walking out, Fisher said: "I didn't come here to be insulted."

Malema bellowed after him: "Go out. Go out. Bastard! Go out. You bloody agent!"

Later, asked to explain why he had ejected the BBC journalist, Malema said: "This is Luthuli House. This is the headquarters of a revolutionary party which has liberated the people of South Africa. It's not a playground. Here you come, you restrain yourself, you behave in a manner that is befitting of being the headquarters of the African National Congress. It's not a beer hall here.

"You don't howl here. Especially when we speak, you behave like you are in an American press conference? It's not America. It's Africa. You must behave in an African way. You are in Rome, you do what the Romans do … if you feel offended by the removal of this gentleman, you are most welcome to walk."

The opposition Democratic Alliance said the incident proved that Malema was "South Africa's Mugabe".

Mpowele Swathe, shadow minister of rural development, said: "Malema's hysterical, conspiracy theory-laden attack on the BBC is painfully reminiscent of the frequent claims by Mugabe that he is the victim of 'malicious propaganda by external forces'.

"His actions, in throwing the journalist out of the press conference, are no different to Mugabe's censorship of the press in Zimbabwe, and his banning of outlets like the BBC from reporting there."

Malema announced that he would heed the ANC's call for restraint and stop singing the apartheid era song that has the words "Shoot the Boer", an incitement seen by some people as causing the recent murder of the white supremacist Eugene Terre'Blanche.