Mordechai Vanunu, the Israeli whistleblower who served 18 years in prison for revealing details of Israel's nuclear weapons programme, should find out whether or not he has been – as he hopes – stripped of his citizenship. As part of his bid to be allowed to leave Israel, he has applied to have his citizenship revoked as should, by law, happen to anyone convicted of treason, as he has been. He would then seek to be allowed finally to leave the country.

Vanunu's attempts to leave Israel have been dragging on for more than seven years now. He was released from prison in 2004, after serving 18 years, and told that he must wait another six months before he could leave the country and must not talk to any foreigners in the meantime. Since then, a cruel game of cat and mouse has been going on, with Vanunu periodically arrested and detained for technical breaches of his conditions. In desperation, he has made this bid to become a non-citizen and thus, he hopes, be allowed to go. The Israeli high court has given the government until Sunday to respond to his appeal.

Over the last few weeks, we have watched as hundreds of Palestinians and a smaller number of Egyptians have been released from jail in Israel and allowed to return home, as part of deals with the Palestinian and Egyptian authorities, in exchange for the Israeli soldier Gilad Shalit. Many of them were convicted of violent offences and their release was opposed by some of the Israeli relatives of their victims.

In contrast, Vanunu is a pacifist. He took the decision to release details of the nuclear programme because he was opposed to nuclear war. He believes that the Palestinian struggle should be one of nonviolent resistance and civil disobedience. The last thing that he would advocate or plan is violence against Israel, however angry he now is at the way he has been treated by the authorities. So why is he not being allowed to leave?

Only the most cynical Israeli politicians and their most supine spokespeople still claim that he might have information that would damage Israel's security. He was a junior technician at the Dimona nuclear facility and he spilled all the beans he had to spill when he gave his story to the Sunday Times in 1986. The refusal to allow him to leave is about punishment, not security. How ironic that the US should be sabre-rattling about Iran's nuclear weapons programme and seeking full disclosure of its plans at the very time that a nuclear whistleblower is seeking his own personal freedom.

When Vanunu emerged, in chaotic scenes, from Shikma jail in Ashkelon in 2004, his opponents made throat-slitting gestures at him and chanted "Death! Death!" They accused his small band of Israeli supporters of being traitors. Many of his enemies would clearly still like to make those death threats a reality. At the time, Vanunu said: "I don't hate Israel. I want to leave Israel."

Since that release, Vanunu's life has been in limbo. He has been offered homes abroad but not allowed to take them up. Eighteen years, 11 of them in solitary confinement, is surely punishment enough, even for the most vindictive of his enemies. But Vanunu is a loose cannon, a stubborn, uncompromising person. He has no government or authority negotiating for his release, even if his supporters have included such voices as Nobel peace prize-winner, Mairead Corrigan Maguire, and Daniel Ellsberg, whose own courageous whistleblowing was one of the factors in bringing an end to the Vietnam war.

Britain has a two-fold responsibility to Vanunu: it was from Britain that he was lured by a Mossad agent to Italy where he was drugged and kidnapped and transported to Israel for his trial and incarceration. And it was to a British newspaper, the Sunday Times, that he entrusted himself.

The moving sight of Shalit being welcomed home and of Palestinian prisoners returning to their families in Gaza and the West Bank should be mirrored now with a picture of Vanunu, a man who has already paid a very heavy price for his principles, walking down to the steps of a plane and on to the tarmac of a country when he is not vilified and threatened.