Malawi's president Bingu wa Mutharika has quit the governing party, saying he is tired of criticism about his high-profile anti-corruption campaign.
President Mutharika accused UDF members of a death plot
The United Democratic Front (UDF) party had been due to decide whether to expel Mr Mutharika for alleged misconduct.
It is the first time a president of Malawi has not been a member of a political party, which is thought to raise several constitutional questions.
Mr Mutharika is expected to form a new party, says the BBC's Raphael Tenthani.
He chose national anti-corruption day to announce his resignation.
"I have decided to resign from the UDF with immediate effect because firstly I no longer have support within the party... my sin as far as the UDF is concerned is because of my anti-corruption stand," he said.
His supporters said Mr Mutharika's tough stance had made him many enemies in government and within his own party.
On Friday, Mr Mutharika sacked three cabinet ministers widely seen as allies of his political rival, former mentor and president Bakili Muluzi.
He has also implicated Mr Muluzi in what he alleged was a plot to kill him.
Analysts say Mr Mutharika's decision does not come as a great surprise as the UDF had come close to expelling him last week.
It is thought Mr Mutharika - who came to power just nine months ago - will form a new party in the coming weeks.
UDF Secretary-General Kennedy Makwangwala told Reuters news agency that the party would now pull out of the government.
"This confirms that he was forming parallel structures as we alleged," he said. "We will now go ahead and pull out of government and join the opposition."