ing party Monday after a long feud with his successor, deepening the cracks that appeared after the party's recent massive electoral losses. In a speech to about 1,000 people, Mahathir said his decision to leave the United Malays National Organization party, or UMNO, was prompted by his lack of confidence in Prime Minister Abdullah Ahmad Badawi.
Mahathir also urged other UMNO members and Cabinet members to quit.
"I am quitting UMNO today. I will only come back when there is a leadership change," Mahathir said. "We can return to UMNO" when Abdullah steps down, he said in the speech in his home state of Kedah.
Mahathir's son Mokhzani confirmed the content of the speech to The Associated Press.
The surprise decision was likely to intensify the crisis for Abdullah, who faces calls from many party members to resign to take responsibility for the party's losses in the March 8 general elections.
Mahathir's call could trigger large-scale desertions by loyalists, which could split the party - one that has been in power since Malaysia's independence from Britain in 1957 - and eventually bring down the government.
The 82-year-old Mahathir had been firing regular barbs at Abdullah and his supporters for more than two years, but had given no indication that he would quit the party. Instead, he had been urging party members to rebel against the prime minister.
"He realizes he cannot fight (Abdullah). The only way is to resign and hopefully force mass resignations from UMNO," said James Chin, a political science professor at Monash university in Malaysia.
However, it is premature to say Mahathir can get sufficient support, he said.
A senior UMNO leader dismissed suggestions that the party would break up, saying Mahathir's departure "is not that important." He indicated that the party was glad to be rid of Mahathir's disruptive influence.
"I welcome his decision. It is high time for him" to leave, said Ahmad Zahid Hamidi, a Cabinet minister and a member of UMNO's supreme council.
"He is old enough to decide. He has every right to do it but he shouldn't urge members to follow him. It's up to the members."
Mahathir appointed Abdullah to succeed him in 2003, when Mahathir retired after 22 years as prime minister. But he remained active in politics, wielding significant influence among the party's grass-roots workers.
By late 2004 Mahathir began accusing Abdullah of nepotism, corruption and inefficiency. Party insiders say Mahathir was angry because many big infrastructure projects he had initiated were canceled by Abdullah.
Some of the allegations of economic mismanagement resonated with Malaysians who were being buffeted by increasing inflation, however. Also, Abdullah's promise to fight corruption had shown few results.
The disenchantment with the government resulted in massive loss of popularity for the ruling National Front coalition, which is dominated by UMNO. It saw its traditional two-thirds majority in Parliament reduced to a simple majority in the March elections.
An opposition alliance of three parties led by former Deputy Prime Minister Anwar Ibrahim won 82 seats in the country's 222-member parliament, up from 19 seats the three parties controlled previously. The coalition also won control of five of Malaysia's 13 states.
