Tasmanian senator Jacqui Lambie has told the Senate that her son is battling an ice addiction, during a debate on proposed welfare cuts.

In an emotional speech, Senator Lambie said there was a "massive problem" with ice in her home state.

"I'm a senator of Australia and I have a 21-year-old son that has a problem with ice," she said on Monday.

"And even with my title, I have no control over my son."

The Tasmanian independent said parents should have more powers to be able to force detox on their children.

"I'm not talking to my son anymore. I'm talking to a drug."

Senator Lambie later told Fairfax Radio that she learned he was "dabbling" in ice a few years ago and that it had become a "chronic issue". She said that until two months ago, he had been living at home, but she had kicked him out after the TV had gone missing.

"You sort of want the tough love, but you want to wrap them up in your arms as well."

The Senator said she now lived in fear that her son would hurt himself or someone else.

"It's on my mind all the time."

Senator Lambie has two sons, Brentyn and Dylan. She has previously spoken of son Dylan's battle with drugs as a teenager as he took on more responsibilities around the home.

Senator Lambie told the ABC last year that when Dylan was a young child, he was her main carer when she had issues with depression and alcohol abuse

"By the time he was 13 he was, he was taking drugs," she said.

Prime Minister Tony Abbott has described ice - which is highly addictive - as "the worse drug problem which we've yet faced".

Senator Lambie made her comments during a debate on the Abbott government's plans to stop welfare payments to people in psychiatric confinement who have also been charged with (but not convicted of) a "serious" offence.

These include murder, manslaughter, rape and other offences relating to loss or serious risk to life.

A person might be in psychiatric confinement if they are having their fitness to stand trial assessed, have been found unfit to stand trial because of mental impairment or have been found not guilty because of mental impairment.

The measure was announced in the mid-year budget update at the end of 2014, and was supposed to start from July 1. It is due to save about $30 million over four years.

It passed the lower house in May and is currently being debated in the Senate, with both Labor and the Greens opposing the measure.

According to the government's explanation of the bill, it aims to change the current practice where "most" people in a psychiatric institution can be considered to be participating in a rehabilitation course and therefore qualify for welfare payments.

The federal government has argued that if a person is in psychiatric confinement, the state or territory government is responsible for their needs.

Speaking against the bill, Senator Lambie said that it was "very easy to take a populist position".

But she said that people had the right to the presumption of innocence until proven guilty.

Senator Lambie added that due to the ice epidemic, more people will be committing crimes due to mental crisis and damage.

During the debate on Monday, Labor said that more work needed to be done on the bill including what would be considered a serious offence.

New ALP senator Jenny McAllister said it set an "unhappy precedent".

But Coalition senator Matt Canavan said that the bill was not vindictive.

"It's simply an adjustment to the way we pay social security."

In response to criticism from Labor and the Greens, Senator Canavan added "there's some notion that we're doing this not because we think it is good ... but because we're simply mean spirited individuals".

"I think I'm a good person, I try and do good in my life."

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