Malaysia's leading opposition figure, Anwar Ibrahim, has been banned from parliament for six months.
Lawmakers voted to suspend Mr Anwar over allegedly misleading statements that a government unity policy was inspired by an Israeli initiative.
Muslim-majority Malaysia has no diplomatic ties with Israel.
Three of Mr Anwar's allies were also suspended, meaning that the opposition now constitutes less than a third of Malaysia's parliament.
Opposition lawmakers are concerned that this means the governing coalition will try to make changes to electoral boundaries ahead of the next polls, reports the BBC's Jennifer Pak, in Kuala Lumpur.
Mr Anwar's suspension - which provoked angry scenes in parliament - relates to remarks he made to lawmakers in March.
He suggested that Prime Minister Najib Razak's push for racial unity under the banner of "1Malaysia" was inspired by an Israeli election campaign in 1999 called "One Israel".
The suspension will bar Mr Anwar from participating in parliamentary debates in the lead-up to the general election, which is widely expected to be called next year.
The three other opposition members were suspended for criticising the probe into Mr Anwar's statements.
Mr Anwar is also currently on trial on sodomy charges - allegations which he denies and says are politically motivated. Sodomy is illegal in Malaysia.
His party made significant gains in the last election in 2008, removing the ruling coalition's long-held two-thirds parliamentary majority.