Broadcaster Alan Jones, along with Harbour Radio and Radio 4BC, has been ordered to pay the court costs of Toowoomba's Wagner family after Mr Jones was ruled to have repeatedly defamed the family on air.

Brisbane Supreme Court Justice Peter Flanagan delivered the costs judgement into the high-profile defamation case on Friday, two months after he found Mr Jones repeatedly defamed Denis, John, Neill and Joe Wagner on-air over several months of broadcasts.

Radio broadcaster Alan Jones arrives at the Supreme Court in Brisbane in May for the defamation trial. Credit:Glenn Hunt

Mr Jones claimed the brothers were responsible for the deaths of 12 people in the 2011 Grantham floods when the wall of a quarry the brothers owned in the Lockyer Valley collapsed.

Over 30 broadcasts between October 2014 and August 2015, Mr Jones made defamatory claims that the family had covered up their "culpability" in the flood deaths and had lobbied Queensland Premier Anastasia Palaszczuk to avoid exposing the "truth".