All credit to Israel's friends in the British Jewish community: they are nothing if not energetic. A matter of months after they gathered for BICOM's We Believe in Israel rally in London, they are now erecting a Big Tent for Israel in Manchester. According to an ad for a spin-off event, once again the focus will be the "delegitimisation of Israel".

I applaud the tirelessness of these campaigners and they are certainly right to take on those who would deny the legitimacy of Israel's existence. But I wonder if they realise that the fight for the Israel they love may also need to take other forms - and not just against the obvious enemies.

Start with the place I visited a week ago: Hebron. What I saw there would shock even those who think they know all there is to know about Israel and its conflict with the Palestinians. The centre of a city of 175,000 people has been utterly emptied, its streets deserted, its shops vacant, thanks to a policy the Israeli army calls "sterilisation" - ensuring the area is clear and safe for Hebron's 800 Jewish settlers.

In what was once a throbbing market district, a place teeming with life, successive restrictions have been placed on Hebron's Palestinian population. A map shows purple roads where no Palestinian cars are permitted, yellow roads where no Palestinian shops are allowed to open and red roads where no Palestinians are even allowed to walk.

I watched an old man, a bag of cement on his shoulder, ascend a steep bypass staircase because his feet were forbidden from going any further along the road. Those unlucky enough to live on a red road have had their front doors sealed: they have to leave their own houses by a back door and climb out via a ladder.

What I saw would shock those who think they know it all

All this has made life so impossible that an estimated 42 per cent of the families who once lived in this central part of town have now moved out.

What they have left behind is eerie. Israelis can walk freely down streets that are barred to Palestinians, surveying the shuttered shops that have been covered with some of the most vile graffiti I have ever seen. The familiar "Death to the Arabs" is there, but so is "You have Arabs, you have mice," the words covered up, but still legible. Perhaps most shocking are the Stars of David, daubed on Arab shopfronts and doors. To see that cherished symbol used to spit in the eye of a population hounded out of their homes is chilling.

All right, some will say, Hebron is an extreme case. Not according to my guide, Yehuda Shaul, a kippah-wearing army reservist who served two long tours in Hebron and who now works with the Breaking the Silence movement which, via the new Yachad organisation, has shown several Anglo-Jewish Zionist youth leaders and synagogue activists around the city. Shaul believes that Hebron simply reveals the reality of the occupation in an intense, distilled form.

But let's say Hebron is too much to stomach. Contemplate instead the bill that would formally make Israeli democracy subordinate to the state's Jewish identity, altering the nation's Basic Law and elevating, in the words of the Knesset's legal adviser, Eyal Yinon, "values such as national strength, honour and Jewish identity, even at the expense of values...such as freedom of expression, the right to equality and minority rights".

It would be consoling if this proposal to turn Israel into a kind of Jewish Prussia - high on nationalism with democracy an afterthought - had at least come from the far right, with no prospects of success. But behind it is Avi Dichter of the supposedly centrist Kadima party.

Or visit the ultra-orthodox Mea She'arim neighbourhood of Jerusalem, where the streets themselves now have a mechitza, men walking on one side of the barrier, women the other. That is until they get on a bus, where the women are required to sit at the back, leaving the seats at the front for the men.

The point is that if the Israel we love is the Jewish, democratic state established in the Declaration of Independence then we need to fight for it. It is under threat and not only from the usual suspects, the hostile media and the "delegitimisers". It is also threatened from within, by Israel's own actions. Put simply, if we are true friends of Israel we would take on those who would transform the country into a place most pro-Israeli Jews in Britain would not even recognise.