MONTREAL — The city's executive committee said Wednesday it's freezing $75 million in non-essential infrastructure contracts amid a kickback scandal involving city engineers and inspectors.

City administrators have also suspended three bureaucrats named by whistleblower Lino Zambito during four days of explosive testimony at the Charbonneau commission into corruption and collusion.

Zambito said bureaucrats manipulate the contracting process by purposely sending incomplete blueprints and other misleading documents to prospective bidders.

The former excavation contractor told the inquiry that city engineer Gilles Surprenant used the scheme to build an $800,000 cost overrun into a sewer project, to the benefit of both men.

Zambito has described wide-ranging collusion schemes that he says drove up the cost of public projects to the detriment of taxpayers while fattening the pockets of businessmen, bureaucrats and the Mafia.

His latest allegations centre around a major sewer-replacement project on St. Laurent Blvd., the main north-south strip running through Montreal.

Zambito said his own engineer noticed that the city blueprints hadn't mentioned the presence of a massive concrete slab under the street.

He brought the omission to the attention of city engineer Gilles Surprenant, who Zambito says told him to keep quiet and submit his bid without taking the slab into account.

"You have to understand one thing: these kinds of operations by engineers are done in order to favour a (particular) entrepreneur," he said.

Zambito says he won the contract and billed the city an extra $800,000 to account for the hidden slab. He has previously testified that Surprenant took a 1% cut off of all contracts.

Surprenant has since retired from the public service.