An Israeli court on Sunday partially lifted a gag order on the case against Bishara, allowing police to announce that its international crimes unit is investigating him.
The statement did not elaborate on why the probe was ordered.
Bishara refused to give details of the continuing investigation but said: "What is the meaning of me spending the coming 10 years proving my innocence to the Israelis?
" ... I am sure that all of the charges would fall but the process that you have to go through is what worries me."
Bishara, who heads the anti-Zionist party Balad, has clashed with Israel's justice system in the past by making "solidarity" trips to Syria and Lebanon and invoking parliamentary immunity to evade prosecution for visiting "enemy states".
"I believe that the larger Arab world as a whole is my homeland," Bishara said. "I am an Arab Palestinian."
Bishara said he had been planning to resign as a parliamentarian because he did not see any further political goals to achieve in that role, but he said: "The investigation made me reconsider [the timing]. In principle I will not reconsider the decision to resign."
|"I believe that the larger Arab world as a whole is my homeland [as] I am an Arab Palestinian"|
Azmi Bishara, leader of Israel's Balad party
An Israeli Arab newspaper report about the resignation has stoked speculation that he might stay abroad to avoid trial, but Bishara denied any plan not to return.
He said: "Of course I will return, but I have postponed it so I can study the issue."
Balad accused Israel of waging a witch-hunt against Bishara and using the court order to prevent him from clearing his name.
In a statement, the party said: "Police are preventing Azmi from addressing the public over these serious charges, which have been leaked to the press and rumour mill. Balad may appeal to the High Court of Justice to get this gag order removed."
A Balad spokesman said Bishara was expected back in the country when his foreign engagements were completed and described his impending resignation as unconnected to the police probe.
Balad holds three of parliament's 120 seats. Its call for Israel to abandon Zionism and merge with Palestinians in the West Bank and Gaza Strip to become a "binational" state resonates with many Israeli Arabs who complain of discrimination from the Jewish majority.
However, Bishara said the way Israel treats Israeli Arabs "makes the issue of self-rule, raised once again, more strongly as a solution for the Arabs of Israel."