The Australian Bar Association has warned the Government that the latest anti-terror bill will "erode cherished freedoms".

The bill allows for dual nationals to lose their citizenship if they have been engaged in terrorism.

But the Bar Association has joined a range of other legal groups in arguing it breaches the constitution.

Association president Fiona McLeod said revocation of citizenship should only occur where a person has been convicted by a court.

"We cannot have public servants making these decisions without due process and these matters being heard by courts," Ms McLeod said.

The Bar Association's submission argues it is unconstitutional to have secret assessments made by public servants.

"The rule of law requires that we see justice and people know what they are being charged of," the submission states.

"They have a right to a fair trial, they have a presumption of innocence, they have a right to present a defence.

"Those are the things in Australia that we hold dear and those are the things that we have to say must be reflected in any act that seeks to strip citizenship away from our citizens."

Parliament's joint intelligence and security committee is examining the bill, including whether it is constitutional.

Shadow Attorney-General Mark Dreyfus told a hearing yesterday there were many legal views that it is not.

"The position is that a large number of the most eminent constitutional lawyers in Australia has told this committee that the bill is unconstitutional or very likely to be struck down by the high court," Mr Dreyfus said.

'Secret process, secret information, secret reports'

Immigration Department head Mike Pezzullo told Mr Dreyfus the Government had legal advice that it is constitutional — but on Ministerial advice it would not be released to the committee.

"The Government has advice to hand that suggests that we are on legally sound ground, it's defensible and it's a common practice — common enough almost to be invariably the case that legal opinions are not made public by way of submission to committees," Mr Pezzullo said.

That frustrated Labor's Senate leader Penny Wong.

"We've had quite a lot of evidence which is putting forward a view as casting doubt as to the constitutionality of this proposed legislation and the only answer the Government has appears to be 'trust us, take us at our word - it's fine'," Senator Wong said.

Mr Dreyfus spelled out his concerns about the bill.

"We've got a secret process conducted by Australian public servants looking at secret classified information, who are going to write a secret report to the secretary of the department, who writes another secret report to the Minister, who signs a form that revokes the Australian citizenship and the Australian never needs to be told and never needs to be given reasons," he said.

"After this secret process is completed, the Minister does not need to inform the Australian whose citizenship has been revoked until the Minister thinks it's appropriate?

"That's right, it's not a requirement of the legislation for the person themselves to be notified."

The joint intelligence and security committee is due to report on the bill at the end of next week.

Australian Security Intelligence Organisation (ASIO) deputy director general Kerri Hartland told the committee being able to strip citizenship from dual nationals would be a useful option.

"We need to have every tool at our disposal, this is but one of those tools but it doesn't stop us doing other things," she said.

Deputy Commissioner of the Federal Police Mike Phelan said he could see it being helpful.

"The deprivation of citizenship for dual nationals, particularly if we are talking about those that are offshore — if it means keeping them offshore — then as far as I am concerned that's once less thing I have to deal with," he said.

Bill would 'further alienate Muslim Australians'

The Muslim Legal Network in New South Wales has echoed the concerns raised by the Bar Association.

The president of the Muslim Legal Network, Zaahir Edries, said the bill would further alienate Australian Muslims.

"There are already significant pieces of legislation available now which protect Australia from the threat of terrorism or those persons who may wish to cause harm on our nation," he said.

"By including further legislation, certain parts of the community just feel that it is a targeted piece of legislation and unfairly so.

"There have been some wide criticisms about the drafting of the bill and the holes that need to be plugged, and that’s really the important aspect.

"Making sure that if such legislation is enacted that there's enough checks and balances to make sure the legal system has a really wide play in what's going on.

"It really shouldn't be just up to the minister to make these decisions."