Malaysian opposition politicians and leading critics of Prime Minister Najib Razak unveiled a fresh campaign aimed at ousting him, after months of attacks over a funding scandal failed to substantially dent his support.

Former premier Mahathir Mohamad and ex-deputy prime minister Muhyiddin Yassin were among those who addressed more than 2,000 people at a convention center in the capital Kuala Lumpur on Sunday, with each of the 18 speakers conveying the same message: Najib must go now. “The wait for two years for the next general elections is too long,” Mahathir said. “Our situation is very bad. We need to recover quickly and two years will be too late.”

Najib is facing his biggest political crisis since coming to power seven years ago as questions linger over $681 million which appeared in his accounts before the last election in 2013, funds the attorney-general said were a donation from the Saudi royal family. Mahathir, the country’s longest serving leader who governed until 2003, has waged a public campaign for months to get Najib out of office.