Jakarta: More than 13,000 Indonesian seaweed farmers will on Wednesday launch a class action in the Federal Court in Sydney against the company responsible for the worst oil spill in the history of Australia's offshore petroleum industry.

Maurice Blackburn Lawyers is seeking hundreds of millions of dollars in compensation for the loss of income it says the farmers suffered when their seaweed plots died after the 2009 Montara oil spill in the Timor Sea.

'A long fight': seaweed farmer Daniel Sanda is in Sydney for the launch of a class action against PTTEP Australasia over the Montara oil spill. Credit:Steven Siewert

"Our investigations show that the operator of the oil rig has a serious case to answer for cutting corners that endangered lives, the environment and the livelihoods of thousands of seaweed farmers," said Maurice Blackburn managing principal Ben Slade.

He said the seaweed farmers, who are from East Nusa Tenggara, one of Indonesia's poorest and most remote provinces, suffered "north of $200 million" in loss of income.