On the one hand they say the extension of basic humanity towards sick asylum seekers trapped in indefinite detention on Manus Island and Nauru would unleash a human tidal wave of would-be economic migrants willing to pay the people traffickers almost any price to make it downunder.

On the other they see no harm in pulling border force vessels from active ocean patrols in a bid to save on fuel costs ahead of next year's election budget.

Incredible as it may seem, given border protection is one of the Morrison government's headline policies, the treasurer doesn't seem to be able to come up with the cash to keep the Border Force fleet at sea defending the realm against the starving, the tortured, the abused and the stateless.

An internal Australian Border Force email that found its way into the media this week said "operational limitations" would be imposed to achieve a saving in the annual fuel budget and, as a result, "ships will cease active patrolling to achieve this fuel saving measure".

It is believed the cuts would apply to the Cape and Bay class vessels patrolling Australia's vulnerable north west coast.

Peter Dutton has disputed the report, saying it is "inaccurate", despite the fact journalists obtained confirmation of the instructions from several insiders.

The revelation makes a mockery of suggestions by Morrison, Dutton and outgoing commander of Operation Sovereign Borders, Air Vice Marshal Stephen Osborne, that the ongoing debate over Dr Kerryn Phelps's private members bill could restart large scale people smuggling.

While Osborne took pains to avoid referencing the bill, which would allow sick asylum seekers detained on Nauru to be brought to Australia for medical treatment if two doctors agreed it was necessary, his meaning was clear on Wednesday.

"We have to be careful of whatever we do," he said. "We are being watched... [people smugglers] will use any means they can, whether they are true or not... all they need is that bit of a lever, that bit of a wedge... to try and sell [the message] that the path to Australia is open again."

Osborne, who offered to brief crossbenchers and other MPs, at the government's request, on the implications of the private members bill last week, did not see fit to mention the curtailment of on-water operations during his exit interviews with the media.

This seems strange given the news the risk of boat turnbacks has been reduced would appear to be far more enticing to people smugglers than possible changes in how medical emergencies in off-shore detention centres could be handled.

The suspension of active patrolling is consistent with recent ABF decisions to slash the number of casual airport staff processing travellers and their luggage over the Christmas period and to suspend a fleet of fast-response patrol boats operating in the Torres Strait.

If people smuggling does resume on a large scale in 2019 these cutbacks, not the Phelps private members bill, will be more likely to be to blame.