Graft-busters posed as secretaries and tea boys to infiltrate vehicle inspection centres, arresting 36 officers for approving cars without even seeing them.

The move came as the government faces mounting criticism of its failure to curb corruption, particularly from opposition leader Anwar Ibrahim who returned to parliament this week in a landslide by-election victory.

Tens of thousands of Malaysian car owners may be forced to re-test their vehicle's roadworthiness after the bust on the Puspakom inspection centres following a three-month undercover operation.

The New Straits Times said undercover officers posed as traffic wardens and administrative staff to discover who was accepting the bribes that were then shared among senior and junior staff.

"All those arrested are believed to have accepted money from vehicle owners," Anti-Corruption Agency (ACA) head Shukri Abdul told the Star daily.

"Eight ringgit would get the thumbs up when inspecting problematic cars while 400 ringgit was charged to 'pass' a vehicle without having it sent to Puspakom," he said.

Latest series of arrests

The bust is the latest in a series of arrests of opposition politicians and senior civil servants in recent weeks as Prime Minister Abdullah Ahmad Badawi seeks to show his ability to tackle corruption.

Abdullah inherited the top job in 2003 and scored a strong election victory a year later with promises of reform, but was criticised for failing to deliver, leading to a drubbing in polls in March this year.

The opposition gained control of five states and a third of parliamentary seats, in the biggest setback ever suffered by the coalition which has ruled for half a century.