Mobil has been fined $288,000 in the Environment Court after thousands of litres of oil spilled into Tauranga Harbour.

Bay of Plenty Regional Council pollution prevention manager Nick Zaman believes the fine was a strong message to companies to respect New Zealand.

The council prosecuted the oil conglomerate under the Resource Management Act.

The oil company was aware a pipe had become rusty and did not act. It then corroded and up to 6000 litres spilled into the sea.

The spill was discovered on April 27, 2015.

READ MORE:

* NZ's oil spill record revealed

* Government awards oil permits in Taranaki

* Mobil apologises for oil spill in Tauranga Harbour

* Greenpeace concerned by NZ oil spill numbers

"This fine is significant, Rena had a bigger impact overall and was fined $300,000," Zaman said.

Mobil has already paid out $1.8 million in clean-up costs so far, he said.