Former Knesset Member Azmi Bishara, who left Israel nearly three weeks ago, is suspected of collaborating with the enemy during the Second Lebanon War last summer.
Bishara is also suspected of several other offenses, including money laundering.
For months, the Shin Bet and the Police International Investigation Unit have been conducting an investigation against the Balad chairman, on suspicion he passed information to a foreign agent.
At the center of the case are large sums of money investigators believe Bishara received from a foreign agent in return for his services.
Bishara was questioned twice in the case and during the last encounter he told interrogators that he intends to leave Israel for a couple of days. He said he would attend a third questioning session soon upon his return to Israel.
When Bishara failed to show up, investigators forwarded the questioning session to April 22, under instructions from Attorney General Menachem Mazuz.
Should Bishara not return to Israel within a week, the court said it would completely lift the gag order on the case and the full details of the investigation would be published.
Bishara has been touring the Arab world since leaving Israel nearly three weeks ago.
Following stops in Jordan and Qatar he submitted his resignation from the Knesset at the Israeli Embassy in Egypt. His resignation took effect on Tuesday, 48 hours after it reached Knesset Speaker Dalia Itzik.
Bishara has insisted he would return to Israel and rebuffed rumors that he intends to settle in an Arab country permanently.
He has also said that he was the victim of a political persecution, accusing the Shin Bet and the Israeli media of waging a campaign to smear his image.
The Petah Tikva Magistrates' Court last week lifted a gag order imposed on the case, but banned the publication of the nature of suspicions against Bishara.
"The suspicions against Bishara prove that Trojan horses, a fifth column, have infiltrated the Knesset. He must be captured, wherever he hides, and brought to justice in Israel," said National Religious Party chairman, MK Zevulun Orlev, Thursday following publication of suspicions against former Balad MK Azmi Bishara.
"Azmi Bishara is only a window on the problem and not the problem itself. Bishara and his friends crossed the line a long time ago, but the state buried its head in the sand," the Yisrael Beiteinu party said in a statement.
"Yisrael Beiteinu had tried, in the past, to prevent this Trojan horse from entering the Knesset, and we can only imagine what damage to the state could have been avoided had our view point been accepted," the statement read.
Likud MK Gilad Erdan stated that the suspicions "confirm that Bishara was never loyal to the State of Israel. He should be treated like an escaped criminal."
MK Otniel Schneller, Kadima, joined the right-wing MKs and said: "The Knesset can only blame itself for allowing itself to sleep with the enemy and enabling a traitor like Bishara serve as a representative of the public.
Schneller said that it would no longer be so easy for Arab parties and representatives to run for the Knesset. "I appeal to the speaker of the House to revoke any privileges that Bishara receives as a former MK and charge him for those he has already received," he added.
Orlev also asked Director that Bishara's severance payments be frozen along with other funds due to him.
MK Yoel Hasson has announced that he will work to have a parliamentary investigation committee look into the affair. "The true face of the worst of Israel's turncoats has been revealed today," said Hasson. "The Knesset must perform self-examination as soon as possible and consider profiling MKs, Arab parties in particular."