The Liberal National Party's candidate for the crucial Longman byelection, Trevor Ruthenberg, has admitted his Queensland parliamentary biography incorrectly claimed he had been awarded the Australian Service Medal.

The medal is awarded for military and other service in peacekeeping operations by the Governor-General on the recommendation of the Chief of the Defence Force.

Prime Minister Malcolm Turnbull during an earlier appearance with the LNP's candidate for Longman, Trevor Ruthenberg. Credit:AAP

Mr Ruthenberg, a former serving corporal in the Royal Australian Air Force, where he trained as an aeronautical ground engineer, told News Corp on Tuesday that if he "screwed up", he apologised.

“It was certainly not intentional and I respect the uniform way too much to claim I earned something I didn’t," Mr Ruthenberg said.