Prime Minister Tony Abbott says Defence Minister David Johnston has his full confidence, but has refused to say if the senator will still be in the role next year.

The Department of Defence has launched an investigation into the release of hospitality receipts, which allegedly reveal the minister and his chief of staff recently spent thousands of dollars on meals and wine for industry players, who were seeking government contracts.

The Prime Minister was asked in Question Time whether Senator Johnston will still be the Defence Minister next year, which Mr Abbott refused to confirm.

"He [Senator Johnston] has my full confidence, he deserves the full confidence of this Parliament," Mr Abbott said.

Senator Johnston told the Upper House a large part of the expenses were related to the ANZAC celebrations in Albany last month.

The Defence Minister said he hosted several foreign dignitaries at the ceremony, which marked the centenary of the departure of the first convoy of Australian and New Zealand troops to fight in World War I.

"France, with a team of approximately eight people, if I remember correctly. From Japan, a team of approximately five people," Senator Johnston said.

"New Zealand had about 10 or 12 people in the party, and of course that's a very sizeable amount of what these relate to."

The Defence Minister refused to comment on reports over the source of the leak.

"It is inappropriate for me to comment on that inquiry," he said.

"However, I would make a general point, that as a senior cabinet minister, and a member of the National Security Council, I require the highest standard of probity, and secure management of information within my office."

Labor senator Stephen Conroy told the Upper House the minister should resign.

"Will he now confirm that this will be his last Question Time as Minister for Defence?" Senator Conroy asked.

Senator Johnston said he would not quit the role of Defence Minister.

Senator Johnston has also been under pressure over the ADF pay offer and his criticism of the government-owned defence builder ASC when he said he would not trust them to "build a canoe".