Victoria's Twelve Apostles now number just seven after another of the rock formations tumbled into the sea off Victoria's west coast on Friday.

A tour operator contacted Parks Victoria early on Friday and reported the small stack had disappeared.

Parks Victoria spokeswoman Jo Curkpatrick later confirmed the collapse.

"It's a small stack just out from the ... Razorback Lookout," she said.

"We have had some fairly stormy weather but it's sort of natural that the stone wears away."

The lookout is located near Loch Ard Gorge and Port Campbell.

Friday's collapse follows the crumbling of another rock formation, the Island Archway, which fell into the sea on June 11.

"Certainly the coast has taken a bit of a beating this winter," Ms Curkpatrick said.

Although another stack had disappeared, she said the formations would still retain their name.

"It will always be the Twelve Apostles," Ms Curkpatrick said.

"It remains unique no matter how many apostles come and go."

The last time one of the Twelve Apostles collapsed was in July 2005.

In 1990 two tourists were stranded on the outer part of London Bridge - another limestone formation off the Great Ocean Road - after one of its two arches collapsed.

No-one was injured, and the tourists were rescued by helicopter.

The apostles started to form up to 20 million years ago as erosion gradually attacked the limestone cliffs of Port Campbell.

- AAP