Israel's top court rejected an appeal by Mordechai Vanunu on Monday to be allowed to leave the country, saying the nuclear whistle-blower, freed in April after 18 years in jail, was still a threat to national security.
The court in Jerusalem said it would publish the reasons for the rejection at a later date.
The Justice Ministry, however, said it might even prosecute Vanunu again if unauthorised interviews he gave foreign media since leaving prison were found to have violated the terms of his release.
"This is a very sad day and shameful day," Vanunu said after the High Court of Justice rejected a petition arguing he had no more secrets to tell about Israel's main atomic reactor at Dimona, and that the travel ban violated his civil rights.
"All the world can see the true face of Israel justice and Israel democracy," he said.
"This is true what we are saying all the time that Israel is not a real democracy and today we are seeing it inside the supreme court of Israel," he added.
Vanunu, 49, was abducted by Israeli agents in Italy and convicted of treason in 1986 after discussing his work as a Dimona technician with Britain's Sunday Times newspaper.
"This is true what we are saying all the time that Israel is not a real democracy and today we are seeing it inside the supreme court of Israel"
Despite 18 years behind bars he remains under strict supervision of the Shin Beth security service and is banned from travelling abroad, talking to foreign nationals without prior authorisation and approaching ports, the airport and border crossings.
His revelations led independent experts to conclude Israel had amassed between 100 and 200 nuclear weapons and all but blew away Israel's policy of "strategic ambiguity" over its non-conventional capabilities.
A convert to Christianity, Vanunu has sequestered himself at a Jerusalem church since he was freed on 21 April. "I want to go abroad and start my life as a free man. If Israel is a democracy it should allow me to do it," he told reporters at the court.
But the government ordered him to be confined to Israel for at least a year and restricted his contacts with foreigners, based on Defence Ministry allegations that he planned to divulge more classified details about Dimona once out of the country.
"Clearly, when a person knowingly breaks the law, he endangers himself anew," state prosecutor Shai Nitzan said on Monday, referring to the "unauthorised press interviews".
Vanunu refutes allegations
According to security sources, Israel alleges Vanunu could name his former Dimona colleagues, putting them at risk of international sanctions or reprisal attacks.
The Defence Ministry has also claimed a jailhouse scrapbook - alleging Vanunu noted technical information on the reactor from memory - as proof that he intends to go public again.
Vanunu, who declined to give names of staff at Dimona to the Sunday Times, said he would continue to withhold them. "After 18 years, no one is interested in these people," he said on Monday.
Vanunu exposed Israel's nuclear
capability in Dimona
Asked about the scrapbook, he described its contents as "basic information with no importance for Israel's security".
The restrictions on Vanunu are subject to government review and could be extended indefinitely.
Supporters fear for Vanunu's safety in Israel, where most people despise him as a traitor and see the country's presumed nuclear capability as an insurance policy against numerically superior Middle East foes.
In an interview conducted by an Israeli intermediary and broadcast by the BBC in early June, Vanunu said he exposed Dimona because he wanted to save Israel from a "new holocaust".
But he has also questioned Israel's right to exist.