Prime Minister Tony Abbott and his Cabinet ministers have refused to answer questions about whether Australian authorities paid people smugglers to take an asylum seeker boat back to Indonesia.

Crew members and passengers of a boat, which was intercepted last month, said officials gave the smugglers thousands of dollars to turn around.

Last week Foreign Minister Julie Bishop and Immigration Minister Peter Dutton both denied the payments had been made, but neither backed up their statements in Question Time on Monday.

Mr Abbott, who fuelled speculation by refusing to confirm or deny the reports over the weekend, said in Parliament: "The very consistent position of this Government has been not to comment on operational details".

Ms Bishop also cited operational matters when refusing to answer a question, and responded to a second query with, "I will not answer the question".

But last week, when asked by the media whether Australian authorities ever paid crew to return asylum seekers, Ms Bishop replied, "no".

Mr Dutton responded similarly last week with a denial, but today instead focused on the steep growth in asylum boats under the previous Labor government.

"This Government had the guts to stop the boats," he told Parliament.

When questioned on ABC's Lateline, Finance Minister Mathias Cormann reiterated the Government's stance.

"We don't comment on security and intelligence matters," he said.

"We have stopped the boats. We have stopped that illegal trade.

"The discipline in not commenting on operational on-water matters was a very important feature of our strategy to stop the boats arriving, to stop the drowning and to stop the budget blow-outs, quite frankly, that were linked from the massive blow-out in illegal boat arrivals under the previous government."

Mr Cormann said Opposition Leader Bill Shorten had not commented either way when asked if Labor ever did a similar thing.

"Bill Shorten refused to comment one way or the other because he pointed to security intelligence matters," he said.

In Parliament, Labor tried but failed to move a censure motion against the Government, with Manager of Opposition Business Tony Burke calling on the Prime Minister to deny the claims.

"A one-word answer will settle this," he said.

"Who would have thought that this bloke could get to the point where he couldn't anymore say the word 'no'?"

No Defence personnel involved: Andrews

Defence Minister Kevin Andrews also side-stepped questions saying he did not want to go "down a rabbit hole", but also stipulated that he did not believe Defence Force personnel were involved.

Space to play or pause, M to mute, left and right arrows to seek, up and down arrows for volume. Watch Duration: 7 minutes 28 seconds 7 m If the government paid people smugglers to return to Indonesia, has it broken the law?

"As far as I am aware this is not arising in relation to Defence Force personnel," Mr Andrews said.

In the Senate, Attorney-General George Brandis gave the commitment the Government always acted "within the law".

"The Abbott Government will observe its legal obligations at all times and we will pursue our successful policy of stopping the boats," he said.

Some legal experts have warned any payment could constitute taxpayer-funded people smuggling and be liable for legal action, however if payments were made by operatives from Australia's intelligence agencies the agents could have legal immunity.

The Intelligence Services Act states that "a staff member or agent of an agency is not subject to any civil or criminal liability for any act done outside Australia if the act is done in the proper performance of a function of the agency"

In particular, the Australian Secret Intelligence Service (ASIS) — a supporting agency for Operation Sovereign Borders — is known to engage in the "disruption" of people smuggling syndicates.

In 2012, ASIS director-general Nick Warner confirmed the service's involvement in a rare public speech.

"ASIS has contributed intelligence and expertise leading to many significant, and unheralded, successes in recent years which have disrupted people smuggling syndicates and their operations," he said.

University of Sydney international law expert Professor Tim Stephens said the law would give agents immunity from prosecution.

"When military agencies are engaged in combat or security agencies are engaged in intelligence and other actives offshore, they are subject to certain privileges , immunities, protection under Australian law to facilitate that kind of activity," he told the ABC's 7.30 program.

Last Friday, Mr Abbott said the Government would "stop the boats by hook or by crook because that's what we've got to do".