An international law expert has raised the prospect that Australian authorities could be accused of people smuggling if it is proven they paid the crew of an asylum seeker boat to return to Indonesia.

Professor of International Law at the Australian National University Don Rothwell said under regional protocols such activity could be tantamount to people smuggling.

Last month, Australian authorities intercepted a boat carrying 65 asylum seekers.

Asylum seekers on board told Indonesian police Australian officials paid the captain and crew members thousands of dollars cash to go back to Indonesia.

Two of the Prime Minister's senior ministers rejected the claim and MP Philip Ruddock last night said the allegations had not been proven.

"[The] point I'm making is that these are allegations. They haven't been tested. We don't know the reliability of them," he told Lateline.

"They are being made essentially by people who are people smugglers and my view is they ought to be dealt with as people smugglers in accordance with Indonesian law."

Tony Abbott refused to confirm or deny the allegations and instead said the Government would stop the boats "by hook or by crook".

"We have used a whole range of measures to stop the boats, because that's what the Australian people elected us to do," he said.

Finance Minister Mathias Cormann has played down the Prime Minister's comments saying he was just sticking to the Government's regular line.

"The Prime Minister has essentially stuck to his very long standing practice not to provide a running commentary on operational matters," he said.

"He didn't confirm or deny, he didn't make a comment one way or the other."

Indonesian authorities are now investigating the claims put forward by asylum seekers.

Professor Rothwell said the episode raised questions because Australia was a party to the 2000 protocol to disrupt people smuggling.

"It's not clear to me at all whether this alleged activity that Australia's engaged in would in any way fit within the framework of the protocol," he said.

"The protocol requires states to engage in cooperative activities to disrupt people smuggling.

"This reported activity is one that has seen Australia seek to pay monies to persons who are allegedly people smugglers to return those asylum seekers at sea back to Indonesia.

"That is not really consistent in any way with regional cooperation, with cooperation with other state parties."

'This is clearly a people smuggling-type activity'

Professor Rothwell said if Australian officials did hand over money to the boat's crew, that in itself could be construed as people smuggling.

"People smuggling is defined with the protocol and to that end the provision of monies to people who are engaged in people smuggling activities to take persons from a place on the high seas to another place, such as Indonesia, is clearly a people smuggling-type activity," he said.

Space to play or pause, M to mute, left and right arrows to seek, up and down arrows for volume. Watch Duration: 10 minutes 36 seconds 10 m Claims of payments have not been tested: Ruddock

"If a state such as Australia is making that payment that would be seen as tantamount to people smuggling.

"Having said that, I'm not sure whether this is a matter that is going to turn so much on the strict legalities of the interpretation of the people smuggling protocol but rather the way in which Australia's regional partners respond to this alleged activity that Australia is engaged in."

Professor Rothwell said the Indonesian government appeared to be taking the allegations seriously.

"They're seeking to confirm whether or not these payments have been made and no doubt if they receive sufficient confirmation of the allegation that's been made we'll no doubt hear from Indonesia in the future about this," he said.

"At either a legal or a policy level this alleged activity that Australia's engaged in is not in any way consistent with Australia cooperating with Indonesia to disrupt and combat people smuggling at sea."