The most costly case involved Mamdouh Habib, who was held in detention in Guantanamo Bay after the United States accused him of involvement in the September 11, 2001 attacks, of training the hijackers, staying at an Al-Qaeda safe house in Afghanistan and helping to transfer chemical weapons.

However, there was insufficient evidence to support these claims and Habib was returned to Australia in 2005.

In May 2009, Habib lost an appeal in the Full Federal Court against a 2007 Administrative Appeals Tribunal (AAT) decision. The tribunal affirmed that former Foreign Affairs minister Alexander Downer had the right to refuse Habib an Australian passport in 2006.

It was revealed in the Senate that up until the end of April nearly $111, 000 had been spent by the Government on the case.

Another Guantanamo Bay detainee, David Hicks, pleaded guilty in 2007 in the US to a charge of providing material support for terrorism and was the first to be convicted at the military tribunal. He was handed a seven-year jail sentence, which was suspended for all but nine months, after taking into consideration the five years already spent at Guantanamo Bay.

Previously, Hicks's legal team lodged documents with the Federal Court of Australia in 2006 arguing that the Government had breached its protective duty to Hicks as an Australian citizen in custody overseas and had failed to request that his incarceration complied with international conventions.

The legal bill amounted to a total cost of about $85, 000.

The Clarke inquiry into the case of Indian doctor Mohamed Haneef, who was wrongly accused of aiding terrorists who attacked the Glasglow airport, cost a total of $11, 000.

Most recently, three Melbourne Tamil men - Aruran Vinayagamoorthy, Sivarajah Yathavan and Arumugam Rajeevan - were accused of raising money in Australia to fund a terrorism campaign in their homeland.

In March, Commonwealth prosecutors told the Victorian Supreme Court they would not be proceeding with nine terrorism charges from the criminal code. Instead the men - who have pleaded not guilty - would be tried on the remaining five charges of breaching the Charter of United Nations Act by making money available to a proscribed organisation.

Nearly $77, 000 had been spent in responding to subpoenas issued in relation to the case.

For responding to subpoenas in the case of Jack Thomas, whose conviction for receiving funds from Al-Qaeda was overturned on appeal, almost $6000 had been spent.

- Sarah Sharples