TEL AVIV, Israel, July 10 (UPI) -- Israel's Shabak security agency has been pretty effective in preventing suicide bombings and other terror attacks. It runs a massive operation protecting the prime minister's life and it is anyone's guess on how good it has been at catching spies. But is it also supposed to "preserve Israel's identity as a Jewish state"?

Or, put it this way: Should a secret intelligence service, in a country that takes pride in its democratic system, spy on Arab citizens who wish to change the state's character?

The issue surfaced after Yuval Diskin who heads the Shabak (better known abroad as the Shin Bet) wrote in an open letter that one of its tasks is to cope with subversion and went on to explain what subversion means.

Subversion "may include also striving to change the state's basic principles canceling ... its Jewish character," he maintained.

It was not a careless mistake. Deputy State Attorney Shai Nitzan, who specializes in security matters, said that "much thought" had gone into that letter. Its contents were "definitely coordinated" with Attorney General Menahem Mazuz to whom the letter was formally addressed. Mazuz agreed to the text and passed it on to human rights groups.

Much about Israel makes it a Jewish state. Some 5.4 million of its 7 million residents are Jews. Its flag bears the Star of David, its coat of arms is a replica of the Menorah that the Romans had taken from the Jewish Temple and paraded back home. Israel's anthem, Declaration of Independence, calendar, holidays and a law that grants every Jew a right to settle in Israel are all part of that Jewish character.

Several organizations who represent Israel's 1.4 million Arabs want to change that. In papers they published this year they sought autonomy over some issues and a right to veto Knesset laws.

Their activity is perfectly legal and Diskin confirmed it. However, it could harm their political parties.

The law bars registration of a party if "its goals or activities, explicitly or implicitly ... reject the State of Israel's existence as a Jewish and democratic state."

The attorney general had tried to invoke that law to ban the Arab Balad Party from running in the elections. To do so he used classified Shabak information, noted Aeyal Gross of Tel Aviv University's Law Department. Balad won, however.

Jaafar Farah, director of an Israeli-Arab advocacy center, Mossawa, told United Press International that Diskin's letter revealed nothing new. Farah said he was sure the Shabak has all along kept tabs on Israeli Arabs.

Diskin's letter was, actually, an open message to the Arab society that, "There are limits to how free you can be to change the situation in this democratic state." It demonstrated "democracy's limits," Farah added.

At the headquarters of the Adalah Legal Center for Arab Minority Rights in Israel, General Director Hassan Jabareen said the attorney general has given the Shabak a green light to pursue Arab citizens, even if what they are doing is completely unrelated to the "security of the state."

Jabareen told UPI Adalah will seek to amend the law that gives the Shabak the right to "preserve the state's character" or at least have Mazuz restrict the security service. In the meantime he was is waiting for a study of how the United States, Canada and European countries cope with the legalities involving their secret services.

The issue has sparked a debate also among Jews. "A democracy must defend itself against those who want to change the state's character through the use of violence and treason," Likud Knesset Member Michael Eitan reportedly said.

When the Shabak gets word of clandestine activity and has "strong reasons to suspect they (the people involved) are planning illegal activity, what should it do? Sit with its hands folded and wait?" asked Nitzan. "Experience shows that not all people use only words," he argued.

The Shabak should protect state security, the regime and its institutions agreed Democracy Institute Professor Mordechai Kremnitzer, but what does all this have to do with "the state's Jewishness?"

Diskin's letter opened the door to misusing the Shabak's authorities especially since the political echelon, the Knesset and the courts do not control it effectively, he added.

"Shabak with an ideological pretense could become an Inquisition and its leader ... Torquemada," warned Haaretz commentator Amir Oren. Tomas de Torquemada had been the Spanish chief inquisitor.