Prime Minister Tony Abbott has entertained the idea of a Cabinet reshuffle in an interview with the ABC's 7.30 program.

It comes as Labor applies more pressure on Mr Abbott to sack his Defence Minister, David Johnston, following allegations the Minister and his chief of staff spent thousands of dollars on meals and wine for industry players who were seeking government contracts.

An investigation is underway by the Defence Department into the leaking of Senator Johnston's hospitality receipts.

Asked in the interview whether it was time to change his frontbench line-up, Mr Abbott said: "At some stage between now and the next election, quite probably, but this is a good frontbench."

Earlier on Thursday during Question Time, the Prime Minister refused to confirm whether Senator Johnston would still be Defence Minister next year.

"He has my full confidence, he deserves the full confidence of this Parliament," Mr Abbott told MPs.

During his 7.30 interview Mr Abbott sang the praises of other Cabinet ministers including Julie Bishop, Scott Morrison and Mathias Cormann.

"Scott Morrison has stopped the boats. Everyone thought that couldn't be done," he said.

"Julie Bishop has had a stellar year as Foreign Minister.

"Mathias Cormann has been an outstanding Finance Minister, done magnificent work, unsung work negotiating with the crossbench in the Senate."

The Prime Minister also defended the performance of his Treasurer, Joe Hockey.

"Joe Hockey has been criticised lately, but I tell you what, I think Joe is going to be one of the great treasurers because he's someone who bounces back and that's what he's doing now," Mr Abbott said.

During the interview Mr Abbott used language similar to that of John Howard's "core and non-core promises", saying that despite breaking some election pledges, he had made good on his "core commitments".

"I know not everyone would agree with me, but I would say that we have kept faith with the Australian people because we have fundamentally honoured the core commitments which were to stop the boats, to repeal the carbon tax, to build the roads," he said.

Mr Howard's formulation of core and non-core promises was not enough to avoid a backlash at the election after a tough 1996 budget.