Ibrahim acknowledged that he now only has days to act before his political momentum seeps away amid efforts by the government to prevent a challenge. He claimed that he has won over 30 government MPs he needs to topple Prime Minister Abdullah Badawi and the ruling party for the first time since independence from Britain half a century ago, The Daily Telegraph reported.
"We have a problem here because we have the numbers but we can't move," Ibrahim said.
For the first time this year, the Malaysian parliament has taken a break for Ramadan, which Ibrahim regards as a "pretext" to prevent a vote of no confidence.
Earlier this month three journalists and an opposition MP were arrested under powers that allow for detention without trial "to protect national security".
Three of the detainees have since been released, but last week the Prime Minister called Anwar a threat to the economy and national security.
"When they say that I am a threat ... then all the rationale for detention is there," said Ibrahim.
"The threat has affected many of our MPs. The threat is working somewhat," he added.
Analysts, and even government supporters, agree that the administration is deeply unpopular because of perceived corruption and a weakening economy.
Ibrahim was a reformist deputy Prime Minister 10 years ago when he was arrested, savagely beaten and jailed on sodomy charges that were later exposed as politically motivated.
He is due in court on Wednesday to face fresh sodomy allegations.
Meanwhile there are moves in the United Malays National Organisation, which controls the government, to remove Badawi as Prime Minister and replace him with his deputy Najib Razak, who is seen as a hardliner.