A photographer, who wishes to remain anonymous, said she saw the boat speeding as it drove over the whales three times. She feared the mammals would be injured or killed.

A series of photographs showing how close the boat came to the southern right whales was snapped the third time it neared the pair.

The woman, who watches the whales every day over the winter months, said the calf was just five weeks old and the mother moved swiftly to protect it as the boat neared.

The Department of Environment, Land, Water and Planning (DELWP) confirmed it was investigating the incident.

“This southern right whale mother and calf have been spotted by whale watchers visiting Portland Bay since July 19 this season,” DELWP acting program manager, resource protection and management, Nathan MacDonald said.

“It is unusual for cow and calf pairs to stay at Portland for so long but it is likely this pair is going to remain in residence for some time now.

“Whale calves are extremely vulnerable to vessel strike so it is crucial that people and boat operators in the harbour keep their distance.”

Under the Wildlife Act 1975, a maximum penalty of $155,460 can be applied for interference that includes harassing, chasing or herding a whale.

Boats must remain 200 metres from whales.