New polling suggests a growing number of voters trust a Labor government would be more capable of handling asylum seekers than the coalition.

"Nobody believes it when this government says that it is doing the right thing by people," Labor frontbencher Julie Collins told reporters in Canberra on Wednesday.

"Nobody believes that indefinite detention is the right thing to do, that's what it shows."

More than a third of voters still fear Labor would "open the floodgates" to asylum seekers if elected, but people are increasingly confident Bill Shorten would either improve or make no difference to existing policy settings.

Mr Shorten has promised to maintain the coalition's boat turn-back policy and preserve offshore detention, but has vowed to pursue third country resettlement more aggressively if his party is elected.

Home Affairs Minister Peter Dutton is looking to highlight apparent divisions between the major parties ahead of five by-elections being held on July 28 and a general election due within a year.

Mr Dutton is warning of boats restarting if Labor returns to controversial asylum seeker policies of the Rudd and Gillard governments.

"As sure as night follows day, if the Labor Party is re-elected at the next election, the boats will restart," he told parliament on Tuesday.

"Those people smugglers are up in Indonesia now rubbing their hands together at the prospect of this leader of the opposition being elected prime minister of this country."

Prime Minister Malcolm Turnbull was considered the best person to handle asylum seekers by 52 per cent of people in December 2017, compared to just 28 per cent support for Mr Shorten.

The latest survey, collated between Thursday and Sunday, showed support levels now stand at 47 per cent for Mr Turnbull and 30 per cent for Mr Shorten, the closest ever margin between the two leaders.

Australian Associated Press