Tough policies preventing settlement in Australia appear to be deterring asylum seekers, with signs of boat arrivals tapering off and reports of people demanding refunds from people smugglers.

Immigration Minister Tony Burke said on Wednesday that large numbers of asylum seekers who had paid upfront for passage to Australia were demanding their money back from smugglers.

And a senior Defence source said that arrivals appeared to be tapering off since Prime Minister Kevin Rudd announced his hardline solution of sending asylum seekers to Papua New Guinea. The highly placed source noted that poor weather was also a factor but was unlikely to account for the extent of the downturn.

With the two major parties set to keep slugging out the immigration battle throughout the election campaign, Mr Burke said there was ''no doubt that the message is getting through'' that asylum seekers would go to PNG rather than be settled in Australia.

The news of a slowing of arrivals comes as the Department of Immigration and Citizenship says via Twitter that another group of asylum seekers, the fourth, has been transferred to Manus Island, bringing to 158 the total number of people taken to detention in PNG since the hardline stance was announced.

One asylum seeker in Indonesia told Fairfax Media that people smugglers could now find ''hardly any'' people willing to board their boats.

Boat arrivals have been down about a quarter since Mr Rudd announced the PNG plan. But that includes a massive spike in the week after the plan was announced, with about 1250 arrivals in those seven days, including six boats with nearly 500 passengers in one day.

The following week there were fewer than 400 arrivals and in the six days since then there have been about 360 arrivals.

The total number of asylum seekers to arrive since Mr Rudd unwound the tough Howard-era policies has now topped 50,000, which Opposition Leader Tony Abbot branded a ''terrible milestone''.

''This has been an absolute disaster for our country,'' he said.

But Mr Burke said the government's hardline policy was getting through, with reports that asylum seekers were demanding their money back from people smugglers en masse in Indonesia.

He said he could not offer more details about the situation in Indonesia because he had only ''specific clearance'' to release some information.

''There is no doubt that the message is getting through. For everything that's been attempted in the past with people smugglers, it's become clear that the only way to affect them is to take their product away and to take their customers away. When I say the demands for money back are widespread, they are absolutely widespread.''

A senior Defence source said there did appear to be a slowing of arrivals, although poor weather to Australia's north was likely having an influence.

''There is an apparent slowing of current vessels but weather and sea states are also impacting on their transits, so a better understanding of the impacts of current policies might be available once the weather clears,'' the source said.

Iranian asylum seeker Bizhan Jahangir reported that people smugglers operating out of Indonesia were already feeling the pinch.

"I know some smugglers here, and they want to find customers, [but] there are no customers now,'' he said. ''They can find hardly any customers, refugees, to go in this situation.

"About three days ago a boat left for Australia, illegally, with only about 30 passengers. You know the capacity of one boat is at least 100 passengers. The smugglers know that from now it will be hard to find new customers."

But it is not only Australia's new policy that is having an impact on the flow of refugees passing through Indonesia. It seems visa restrictions are making it harder for Iranian refugees, at least, to use the country as a staging post on their route to Australia.

"Iranians are finding it hard to get Indonesian visas. They have to come to Indonesia illegally. They have to fly first to Malaysia, then perhaps get a boat to Indonesia. It's very hard for Iranians. Iranians don't want to come to Indonesia. They will find other ways to go to other countries, not Australia.''

Coalition immigration spokesman Scott Morrison said: ''Minister Burke will talk and talk, but at the end of the day the arrangement that he's agreed with Papua New Guinea doesn't back up his big, bold claims.''

With Igor O'Neill in Jakarta