A Toronto lawyer says he was shocked to learn that intelligence officials were intercepting his phone calls with two clients who had been labelled national security threats.

Rocco Galati told The Canadian Press that he had a long-standing hunch that his calls with Mohamed Mahjoub and Mahmoud Jaballah were being monitored, but was stunned to find evidence that his suspicions were true.

"I couldn't believe the degree to which the judicial process had been corrupted," Galati told CP outside Federal Court on Wednesday.

Mahjoub and Jaballah are the recipients of separate national security certificates, which allow the government to detain or remove foreign nationals who “pose a serious threat” to Canada.

Lawyers for Mahjoub have returned to court in an effort to prove that security officials breached their client’s privilege to communicate privately with his legal team.

The Canadian Security Intelligence Service admitted to listening in on Mahjoub's calls with his lawyers in 2008, but only to monitor his bail conditions.

A judge swiftly ordered an end to the practice after Mahjoub’s lawyers argued that their client never agreed to waive solicitor-client privilege, which guarantees him access to confidential communication with his lawyers.

Now, Mahjoub’s lawyers say they’ve obtained information that proves CSIS and the Canada Border Services Agency have been intercepting communication between Mahjoub and his lawyers all along.

Mahjoub was arrested in June 2000 after the federal government labelled him a threat to national security, alleging he was a high-ranking member of a terrorist group. Since then, he has spent more than a decade in prison or under house arrest without charge.

Mahjoub’s lawyers appeared in a Toronto courtroom on Wednesday to present evidence that the Canadian Security Intelligence Service (CSIS) violated solicitor-client privilege.

“We’ve received documents from the Department of Justice that includes information they simply could not have had without illegal access to confidential conversations between Mr. Mahjoub, his family and his lawyers,” Lawyer Yavar Hameed said in a prepared statement.

Court was expected to hear conversations that were allegedly obtained illegally.

Galati, who specializes in cases related to terrorism, appeared on the witness stand to testify about his correspondence with Mahjoub.Galati represented Mahjoub between 2000 and 2003.

Complicating matters, CSIS was forced to reissue Mahjoub’s security certificate after the Supreme Court of Canada ruled that the certificate process was unconstitutional in 2007.

Mahjoub, a Toronto resident and father of three, is fighting to have the certificate revoked.

But what started as a quest to clear his name has branched off into a multifaceted case, touching upon the ethics of security certificates and the validity of information derived by torture.

Documents obtained by the Canadian Press show CSIS was aware that most of the information it used to brand Mahjoub as a security threat was obtained by agencies linked to torture.

Last summer, Federal Court Justice Edmond Blanchard ordered 11 federal lawyers and assistants off of the case after the government inadvertently took Mahjoub’s confidential legal files.

Mahjoub’s lawyers argued that the incident damaged their client’s right to a fair trial, accusing Ottawa of violating both solicitor-client privilege and litigation privilege, which prevents premature disclosure of documents that may be used in a court case.

After the document seizure, Blanchard would not stay proceedings, noting that the incident “although negligent, was unintentional.” He did, however, say Mahjoub’s legal team could use the incident and subsequent delays to claim an abuse of process.

Recently, the Federal Court ruled that abstracts of wiretap information used against Mahjoub had to be tossed out because CSIS destroyed the original records.

Mahjoub, who is on release from prison, had his house-arrest conditions eased last February.

With files from The Canadian Press