Opposition Leader Tony Abbott has accused asylum seekers who threaten to hurt themselves of blackmail.

The Government has confirmed that up to 36 asylum seekers, rescued by a Singapore-bound merchant vessel last week, were taken to Christmas Island after threatening to harm themselves.

The Coalition has called for Australian military intervention on the high seas in such cases, evoking the case of the MV Tampa in 2001.

Mr Abbott says the Coalition will not be "played for mugs by the people smugglers and their customers".

"The Australian Government should not be expected to take responsibility for foolish actions by non-citizens. We just can't be expected to take responsibility for that," he said.

"People should not threaten acts of self-harm, and the Australian Government will not be blackmailed, should not be blackmailed by people who are threatening to do something that they should never do."

The Government says the merchant ship intended to take the asylum seekers to Indonesia but was forced to turn back towards the Australian territory because of a threat of "self harm".

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The Government says the Australian Federal Police is investigating and the asylum seekers may face criminal charges.

Opposition immigration spokesman Scott Morrison says a vessel in that situation is "effectively being taken over".

He says Australian forces should step in.

"People here in this situation are basically taking advantage of the safety of life at sea convention," he told Sky News.

"They get rescued by a ship that comes to their aid and they then threaten them with their own suicide to demand that they be taken to Australia.

"People who are going to try this on, they should be stopped.

"What the Australian Government should be doing is letting merchant vessels know that if they are in that situation, that an Australian naval or Customs vessel would come to their aid and support them.

"What the Government has done is the reverse-Tampa effect. They've just welcomed people to Australia, they've endorsed this behaviour time and time again."

Decision about safety of life at sea

A spokeswoman for the Australian Maritime Safety Authority says it "agreed to the [ship's] Master's request to take the asylum seekers to Christmas Island, after he raised concerns about the safety and security of the asylum seekers and his crew."

Home Affairs Minister Jason Clare says it is not the job of politicians to decide safety of life at sea issues.

"It is the job of people in uniform to make these decisions not politicians," he said.

"If there was a siege and there were hostages it wouldn't be right for politicians to tell police to go in all guns blazing; it is not right for politicians to tell people in uniforms or captains of ships what to do.

"These decisions are made by the captain of the ship where there's a safety of life at sea issue, and they're made by people in uniform. They shouldn't be made by politicians."

Morrison says sending in SAS a possibility

In 2001, the Norwegian cargo ship MV Tampa rescued nearly 500 asylum seekers north-west of Christmas Island and was boarded by SAS troops on the command of then-prime minister John Howard.

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The so-called Tampa affair was the catalyst for a new border protection regime in Australia and, coupled with the attacks of September 11, is credited with returning the Coalition to office with a comfortable win.

Mr Morrison says it would be possible to again send in the SAS.

"That's what John Howard did and that's the message that was sent to the region," he said.

"You've got to be prepared to do this sort of stuff," he later added.

Immigration Minister Tony Burke has agreed the asylum seekers took "effective control of the vessel".

"There's a series of potential criminal actions that may well be part of that," he told ABC News 24.

"The master of the vessel ended up going to Christmas Island with no original intention of doing so under pressure from the passengers.

"The view is very simple - if people have acted criminally then it must not be to their advantage."

The asylum seekers involved are in detention on Christmas Island.