The boat was about halfway between Indonesia and Christmas Island on Sunday when it sent a distress call at about 8am, with reports it was sinking and HMAS Parramatta "rendered assistance".

It came as a second boat, carrying about 48 people and three crew was intercepted by HMAS Bundaberg north-west of Christmas Island on Sunday.

The two most recent boats are the first to arrive after a four day break. But on Monday, Opposition Leader Tony Abbott said he did not think that boat arrivals were dropping off in the wake of the Rudd government's Papua New Guinea plan, announced in July.

"I accept that there will be surges and there will be lulls," he told reporters in Sydney.

"The problem is that this government's [PNG plan] is already overwhelmed by the tide of boat arrivals since Mr Rudd first made the announcement," he said.

While addressing reporters in northern NSW on Monday, Mr Rudd dismissed questions about his PNG plan, including reports over the weekend that PNG had not agreed to resettle all asylum seekers in the country.

"It's very plain, it's there in black and white in the agreement … that I signed with Prime Minister Peter O'Neill," the Prime Minister said.

Mr Rudd said that he had not heard of an alternative to his resettlement plan that would reduce the number of people drowning at sea.

“It is the right conclusion," he said.

As the debate over asylum seekers continued, Mr Abbott also hit out at the latest union campaign against 457 visas - saying Mr Rudd should "dissociate himself" from the ads.

The Construction, Forestry, Mining and Energy Union has launched a campaign that claims the Coalition wants to expand the 457 visa program.

"[457 visa holders] come into this country and they work and they pay taxes from day one ... They aren't stealing our jobs, they're building our country, and it appalls me, it really appalls me that the unions and Mr Rudd are running this campaign effectively to demonise the skilled migrants upon whose backs our country has been built," Mr Abbott said.

"Just about every Australian is a migrant or a descendent of migrants and in fact we should be honouring and cherishing the contribution of the migrants who come to this country legally, the right way."

Former Labor national secretary Warren Mundine has also slammed the 457 campaign.

"If you want to know why I quit the Labor Party just look the bigoted 457 campaigns on TV. It harps back to the White Australia Policy of old," he posted on Twitter.

Mr Mundine quit the Labor Party in 2012, and earlier this month it was announced that he would head a new indigenous advisory board for Mr Abbott, should the Coalition be elected in September.

With Georgina Mitchell