"The defendant denies any breach, has pleaded affirmative defences and has counter-claimed for alleged unpaid commissions which he says the plaintiff owes him," Associate Judge Doogue said.
Bambury said today that he did not want to comment on the details of the case.
Jensen said he had filed "an extremely full statement of defence" when contacted at his gallery in Sydney.
"It's a breakdown in a relationship that's 25 year's old," said Jensen, who has also published writing on Bambury.
"He and I were the closest of friends for 25 years...it's a remarkably, kind of, lamentable and sad end to a long working relationship."
Christchurch-born Bambury, who is in his early 60s, is considered one of New Zealand's leading and most-respected abstract artists.
Herald art writer T J McNamara said Bambury's work has "always been rather severe, minimal abstraction".
"He is much admired. He gets in all the books on New Zealand art," McNamara said.
Jensen, who is a director of the Fox/Jensen gallery in Newmarket, opened another in Sydney in 2011.