Oil giant Mobil has escaped a $10 million bill for the cleanup of heavily contaminated prime land on Auckland's waterfront.

It has won an appeal in the Supreme Court.

That means Auckland's waterfront development arm now has to pay Mobil close to a million dollars in costs after its failed attempts to get it to foot the bill.

Mobil's lease for two sites at Wynyard Quarter ended in 2011, and the land was found to be heavily contaminated.

It was found the company wasn't solely responsible but Waterfront Auckland claimed Mobil didn't give the land back in the right condition.

The ruling comes after a string of court battles.

Waterfront Auckland - now called Panuku Development Auckland - challenged the decision original decision in favour of Mobil, and last year the Court of Appeal reversed it, awarding a $10 million judgment to the council-controlled organisation.

The Supreme Court - in a just released decision - overturned the Court of Appeal's decision and found in Mobil's favour.