South Africa's governing ANC has suspended youth leader Julius Malema from the party for five years.
He was found guilty of bringing the party into disrepute and ordered to step down as youth league president.
Once a close ally of President Jacob Zuma, Mr Malema has become one of his strongest critics, accusing him of ignoring poor South Africans who helped bring him to power in 2009.
"The gloves are off," said Mr Malema who plans to appeal against the ruling.
"Let the enemy enjoy, but that victory will not last," he was quoted as saying by state radio, SAFM.
"We will be liberated by Mangaung 2012," said Mr Malema, referring to the ruling party's elective and policy making conference to be held next year.
"Real leaders of the ANC must now stand up in defence of the ANC," he said.
"We will remain resolute. We will continue to fight moving forward, because the ANC is our home, and we have not any home except the African National Congress," he told about 500 supporters, the AFP news agency reported.
He was speaking in his home town, Polokwane, where he had been sitting a university exam in political studies while the ANC's disciplinary committee was announcing that he and five other top ANC youth league officials had been suspended.
Boost for Zuma
The BBC's Milton Nkosi says the verdict boosts Mr Zuma's re-election bid.
Mr Malema, 30, wants Mr Zuma replaced as party leader ahead of the 2014 elections and replaced with deputy leader Kgalema Motlanthe.
Our correspondent says it is now difficult to see how Mr Malema can affect the ANC leadership contest next year, but Mr Zuma is not certain of a second term and other critics remain.
Mr Malema has 14 days to appeal, but was already suspended for his statements on Zimbabwe and so must vacate his position as youth league leader immediately.
If he loses his appeal, the ANC will elect a new youth league leader.
After Mr Malema's suspension, an ANC spokesperson said: "Disciplinary procedures are not meant to end anybody's political career, they are meant to correct behaviour."
But unless the period of his suspension is reduced on appeal, he would be too old to return as the head of the Youth League if he returns to the party in five years.
The party celebrates its 100th anniversary in January 2012 and our correspondent says ANC officials are determined to show that Africa's oldest liberation movement will not be dictated to by a young, unruly leader.
Mr Malema was found guilty of three of the four charges brought against him, which included disrupting a national ANC meeting, and of bringing the party into disrepute by calling for regime change in democratic Botswana - a position which contravenes party and government policy.
He was also found guilty of provoking serious divisions within the party by praising Thabo Mbeki, who was sacked as party leader and then ousted as South Africa's president by the ANC three years ago.
Mr Malema has been cleared of sowing racism or political intolerance.
"Ill-discipline is not a cure for frustration," said Derek Hanekom, who led the disciplinary hearing.
"Such disobedience undermined the effectiveness of the ANC."
There has been tight security outside the ANC headquarters in central Johannesburg, but none of the large crowds of ANC Youth League members seen when the hearing opened in August.
Thousands of Mr Malema's supporters clashed with police and some were seen burning T-shirts bearing Mr Zuma's face.
Mr Malema is a hugely divisive figure in South Africa after making a series of controversial statements.
He has previously been found guilty of using hate speech by singing an anti-apartheid song Shoot the Boer [white farmer], which has since been banned.
He once vowed to "kill for Zuma" and was also disciplined for saying a woman who said she had been raped by Mr Zuma had had "a nice time". Mr Zuma was acquitted of the charges.
In May 2010, he was made to apologise publicly following a controversial trip to Zimbabwe where he declared the ANC's support for President Mugabe at a time when Mr Zuma was mediating between the country's coalition members.
He is also being investigated by an anti-corruption unit over allegations of irregularities in the awarding of government contracts to companies in his home province of Limpopo. He denies any wrongdoing.
Youth League spokesman Floyd Shivambu was suspended for three years for the Botswana statements and for swearing at a journalist.
Four other top Youth League officials were also found guilty on various charges, but were granted suspended sentences - meaning they retain their ANC membership unless they offend again.