A party in Malaysia's ruling coalition said Wednesday it plans to seek a vote of no-confidence against the prime minister in an unprecedented act of rebellion that could force him to resign or call for new elections.

The Sabah Progressive Party, a member of the 14-party ruling National Front coalition, said its two federal legislators would back a motion of no-confidence against Prime Minister Abdullah Ahmad Badawi when Parliament resumes Monday.

"We have lost confidence in the prime minister of Malaysia," party leader Yong Teck Lee told a news conference in Kota Kinabalu, the capital of Sabah state on Borneo island.

The lawmakers must first convince Parliament's speaker to allow a no-confidence vote, but their biggest challenge will be getting enough legislators to support the motion.

The move would be a first in Malaysia's political history: No Malaysian prime minister has ever faced a vote of no-confidence presented by a member of his own coalition before.

The National Front has 140 lawmakers in the 222-member Parliament, enough to defeat any vote against Abdullah. But after the front's dismal performance in March 8 elections _ largely blamed on Abdullah's leadership _ there is no guarantee that all ruling coalition lawmakers would want to protect him.

If Abdullah loses a no-confidence vote, he must resign or ask the constitutional monarch to dissolve Parliament, which would pave the way for new elections. If the king refuses to dissolve Parliament, the Cabinet must resign and the king would appoint a new prime minister.

Yong said the two Sabah party lawmakers will either present the no-confidence motion or let the opposition do so. His party has long accused the National Front of neglecting Sabah's problems, such as poverty and illegal immigrants.

He said his party would also discuss whether to leave the National Front on Friday. He declined to speculate on whether it would join the opposition, but acknowledged having met with opposition leader Anwar Ibrahim twice in recent months.

Political observers say other National Front parties may follow if Yong's group quits, potentially destabilizing the government if they join an opposition alliance that needs 30 more seats in Parliament to topple Abdullah's administration.

Abdullah sought to win favor with Sabah's leaders recently by pledging $300 million to develop the state's rural provinces and setting up a panel to curb rising numbers of illegal immigrants from the Philippines and Indonesia. But some Sabah politicians say Abdullah should have done more.

The ruling coalition lost its two-thirds parliamentary majority in the March 8 elections for only the second time since independence in 1957, and ceded control of five states to the opposition for the first time.