Boskalis, the company hired to dredge the bay if channel deepening goes ahead, is under scrutiny over three major accidents, including two in the past few months.

Three people died when Boskalis vessel Nautilus capsized during dredging in the port of Pointe-Noir, in the Republic of Congo, last November.

Another of the Dutch firm's vessels was involved in a collision in the Chinese port of Tianjin on March 7 this year.

And one of its dredgers sank while at a ship repair yard in the United Arab Emirates in January, 2003.

"The Heads are acknowledged as one of the most dangerous waters in the world, so the safety record of any ship operator must be unblemished," said Christopher Collins, executive officer of Victoria anglers body VRFish.

"We need the Port of Melbourne Corporation to unequivocally produce a clean bill of health for this operator."

"This company was chosen after going through the normal government processes," a spokesman for Ports Minister Tim Pallas said.

Boskalis defended its safety record.

"Boskalis operates over 300 vessels across the world and we execute hundreds of projects every year. Unfortunately, accidents sometimes occur," Boskalis spokesman Roel Berends said.