The government's justification for keeping an Egyptian suspected of terrorist involvement under rigid house arrest is based on false information obtained by torture, the man said Monday.

Speaking outside Federal Court, Mohamed Zeki Mahjoub said his situation has caused him and his family great distress.

"It is very harsh for me and for my family," Mahjoub said.

"All of us are suffering. I feel I've been treated very badly in this society."

In court, a witness for Canada's spy agency outlined that Mahjoub should remain under stringent house arrest because he poses a threat to national security.

The agent, who can only be identified as Witness No. 4, drafted an updated threat assessment last month indicating Mahjoub remained potentially dangerous.

The assessment is based on Mahjoub's "background and previous activities," including being an active senior member of an al-Qaeda-affiliated terrorist group, the witness said.

"He was not a pawn or follower," said Witness No. 4, who testified from a courtroom in Ottawa.

"He has a certain pedigree. He has a certain deeply held belief system."

Detained under security certificate

Mahjoub, 51, of Toronto, came to Canada in 1995. He was detained in 2000 under a national security certificate, which allows for indefinite detention of a foreigner without charge or trial.

He spent more than seven years since that in jail, and the rest of the time has been under stringent house arrest that involves wearing a tracking device, keeping a curfew and constant surveillance of his residence.

One expert submission to the court described the release conditions as among "the most invasive in Canadian legal history — prying into every recess" of his life.

The government alleges that Mahjoub recruited others to take part in assassination cells in Egypt, and was involved in the bombing of the Egyptian embassy in Islamabad in 1995.

Ottawa wants to send the married father back to Egypt, but he has staved off deportation by arguing he would be tortured there if sent back.

He has previously argued successfully that some of the information being used against him in Canadian courts was derived from torture.

Witness No. 4 did concede the service has no fresh information to justify its view that Mahjoub remains a threat that can only be mitigated by his detention or conditions of his release.

However, the agent told Judge Edmond Blanchard that the Canadian Security Intelligence Service has seen no evidence that Mahjoub has ever renounced his extremist beliefs.

"He has the potential to re-engage in those activities," Witness No. 4 said.

Because the current situation in Egypt is "dynamic" and "tumultuous," it is "rife with opportunity" for people to resort to violence for political and religious objectives, he said.

Hearing to last several days

In cross-examination, lawyer Paul Slansky pressed the agent on what gave him "reasonable" grounds to conclude Mahjoub still posed a threat.

"I'm not a lawyer," the agent retorted at one point.

Mahjoub is still contesting the reasonableness of the national security certificate itself in a separate hearing.

"The threat assessment itself didn't allege I'm dangerous to Canadian society or any other person," said Mahjoub, who heard the agent testify via a video-linked courtroom monitor in Toronto.

Mahjoub and members of the public could not see the agent.

The hearing is expected to last for several more days.