TasPorts says the incident, which occurred in January at Devonport in the state's northwest, continues to cause significant disruption.

Environmental authorities and TasPorts were forced to contain 69,000 litres of diesel fuel and other oil that was aboard the two sunken tugs.

TasPorts on Thursday said it had begun Federal Court proceedings against CSL Australia, owners of the cement carrier Goliath.

TasPorts chief executive Anthony Donald said the company would attempt to reach an acceptable settlement with CSL Australia in the short to medium term.

"It is not TasPorts' intention to progress the proceedings unless and until it becomes necessary to do so, but we believe that the commencement of proceedings is a prudent step to take to protect our rights," he said.

"At this time, completion of the clean-up operation remains TasPorts' focus.

"We are continuing to do everything we possibly can to minimise disruption to port users and other stakeholders."

TasPorts said the complicated clean-up, including removal of the tugs' wreckage, is at an advanced stage.

Because of the oil and fuel spill, Tasmania's Environment Protection Authority in early February temporarily limited access to parts of the Mersey River and warned people not to eat fish from the river.

A preliminary Australian Transport Safety Bureau report released in early May found Goliath was not in the correct steering mode in the lead up to the collision.

"As a company committed to the Australian shipping industry, with Australian ships and Australian crews, we sincerely regret that the incident occurred," a CSL Australia spokeswoman said.

"The safety of crew members and the community, and the protection of the environment remain our top priorities."

Australian Associated Press