Already facing court action by the Environment Protection Authority of Victoria over an oil spill into Corio Bay in April, Shell is now also being investigated over a separate incident in May, today’s Age newspaper reports.

In addition, an EPA audit has found that Shell has no documented plan to deal with a tanker hitting the refinery jetty, an accident that could release hundreds of thousands of litres of hydrocarbons into Corio Bay.

There was an unacceptably high risk that spilt oil could damage the marine fauna and the shore surrounding the jetty, the audit found.

Shell Geelong refinery spokeswoman Joan McGovern confirmed to The Age that the hazard analysis did not take into account a ship hitting the jetty.

She said the refinery's performance had improved since 2003, when there were 282 recorded licence breaches. The number fell to 112 last year.

But EPA executive director of regional services, Bruce Dawson, told The Age that Shell remained in breach of its environmental licence because of continued oil leaks and spills, visible air emissions and odour from the refinery.

The EPA audit, ordered after leaks at the jetty in 2003, found that the $12 million Shell spent since then had improved jetty pipes. But Shell still needed to spend a lot more to comply with its EPA licence, according to Dawson.