Immigration Minister Scott Morrison has revealed Australia unsuccessfully tried to get India to take 157 asylum seekers while they were being held on a Customs ship for almost a month.

The Sri Lankan Tamil asylum seekers, including at least 37 children, were transferred to the Curtin Detention Centre several days ago, breaking long-standing government policy.

They had set sail from the Indian state of Pondicherry in mid-June in a bid to seek Australia's protection.

For weeks the Minister had refused to acknowledge the asylum seekers and what was happening to them.

Mr Morrison revealed on 7.30 that secret negotiations had been underway with the Indian government.

"We discussed three options," he said.

"One was that they could be taken to India where the process I've talked about, their identity and so on could be assessed. That was not accepted by India," he said.

The asylum seekers have been transferred from Cocos Islands to Curtin for questioning. ( AAP: Brad Waugh )

After Australia failed to get the Indian government to take the Tamil asylum seekers, Mr Morrison said attempts were made to get Indian consular officials into Customs ship Ocean Protector.

On board identity and nationality checks proved logistically difficult so the asylum seekers, who the Immigration Minister said were "economic migrants", were taken to the remote Curtin Detention Centre in Western Australia.

"We'll see how it goes but if the outcome of this is that no-one chooses to talk to Indian consular officials, then the Government's policy is very clear," Mr Morrison told 7.30.

"They will go to offshore processing and that's where their claims will be assessed."

No discussion with Sri Lankan government, Morrison says

Mr Morrison said there was no discussion with the Sri Lankan government about taking back the people on the boat.

"I'll tell you why - that voyage did not come from Sri Lanka. It came from India," he said.

"People were living in India or had transited through India."

Space to play or pause, M to mute, left and right arrows to seek, up and down arrows for volume. Watch Duration: 4 minutes 49 seconds 4 m 49 s Refugee advocates call Government to hear claims of asylum seekers after weeks at sea

Mr Morrison refused to confirm whether attempts had been made to return the asylum seekers to India using Australian orange lifeboats.

The lifeboats have been used several times to return asylum seekers to Indonesia, which has irritated the government of Australia's northern neighbour.

"The Government always uses all of our operational options available to us," Mr Morrison said.

"I always reserve those options to us, as does Lieutenant-General Campbell. But when and where we do this - those are operational matters."

The Immigration Minister says the Tamils' time in Curtin is temporary and they will not have asylum claims assessed on the mainland.

"They will never ever be resettled in Australia and that will be the outcome, nor will they ever be able to probably go back to India again," he said.

Indian consular officials are expected to be at the detention centre within days to help determine the asylum seekers' identity and residency.

The Indian High Commission has now received an official invitation by Australia to interview the Tamils and both parties are now sorting out arrangements.