I want to begin by saying what this speech is not.

It's not an attempt to deflect attention from the pressing urgency of achieving an agreement to the Israeli-Palestinian conflict.

It's not an argument which posits that Israel is always right and should be allowed to act with impunity.

And it's not intended to diminish the need to resolve the complex issues of borders and settlements; of refugees; and of Jerusalem.

So let me begin by re-iterating the need for both sides to return to the negotiating table to make the painful and necessary compromises that will be required to end this conflict for good.

Whenever I say something supportive of Israel I am almost always challenged to say something critical too. It's as if I have to buy permission to say something positive David Cairns MP

In all of the forums I have been involved with LFI, and in every meeting in which I have participated, this has been the consistent message. It has been conveyed to Israeli politicians of all parties, and every Palestinian leader of recent years.

And, if needs be, in months and years ahead, LFI will continue to focus on the need to resolve this tragic conflict, which has already claimed too many lives and caused too much grief.

But tonight I want to offer another message - not in contradiction to the first, but complementary. And the message is this: in a time of upheaval and unrest we will never find a just and lasting agreement if we forget or overlook the fact that that Israel is the only regional exemplar, not just of democracy but of social democracy. Its values are rooted in left-of-centre principles. It is a place where

• women enjoy equality;

• the LGBT community flourishes;

• the media is unfettered and critical;

• an independent judiciary protects the powerless from the powerful;

• where trade unions are well-organised and strong;

• educational excellence and scientific innovation are pursued;

• religious minorities are free to practise their creeds;

• a welfare state supports the poor and marginalised;

• and, yes, it is a fully functioning, vibrant, participatory democracy.

And the reason I feel the need to deliver this message tonight is that the failure to make progress in securing an agreement to end the conflict, bolstered by opposition to the very concept of Israel, has resulted in not just reasonable criticism of Israel's conduct and behaviour, but in increasing attempts to de-legitimise the Israeli state; and the advocacy of a policy which would could see its demise as a social democratic beacon.

Years ago, when I first became involved with LFI the two-state solution was accepted by mainstream Israelis and Palestinians alike. It was rejected by the Israeli right and by Islamist extremists.

Today much of the Israeli right now accepts the principle of a two-state solution, which is obviously welcome, and it is still the goal of the Palestinian leadership in the West Bank. But Hamas in Gaza remains committed to the destruction of Israel by force, and the so-called One-State solution is becoming much more mainstream. For some, this popularity is born from frustration but, let's be absolutely clear: the one state model means the demise of the Jewish state. It is the end of the dream of national self-determination for the Jewish people. And that is why Hamas wants it.

And why does this matter? It matters for two reasons: the first is the fact of the state of Israel, how and why it came to be. And the second is the nature of the state of Israel and the values that it has come, through time, to embody.

As recently as 2001 the Guardian, not always Israel's most staunch supporter, called the establishment of the state of Israel a "moral necessity".

This was the long held belief of the British left; and not just the left, but the left of the left: writing in 1968 Eric Heffer said: "When Israel was established by resolution of the United Nations, like most Socialists, I was delighted."

Why the delight among Socialists? It was their belief in the right of self-determination for the Jewish people, the searing experience of World War II, and the overthrow of colonial rule that galvanised left-wing support for David Ben Gurion's declaration.

It was precisely these reasons that gave some on the Labour right, most notably the formidable figure of Foreign Secretary Ernie Bevin, cause for concern.

The right of self-determination for the Jewish people was a matter of progressive principle and conscience in 1948 and it should remain so today. And it is because I believe in the right of Jewish self-determination that I support Palestinian self-determination too.

On both sides, we should see the other's goal as an essential part of our success, not a fundamental barrier to it.

But it was not just the fact of the Jewish state that won it support from the left; it was the type of state it was to be: a socialist, egalitarian society, one where Labour would be the natural party of Government.

The Declaration of Independence speaks of an Israel which "will ensure complete equality of social and political rights to all its inhabitants irrespective of religion, race or sex; it will guarantee freedom of religion, conscience, language, education and culture". Or as we might put it today - this would be a progressive country.

And so it remains.

But failure to secure agreement to the conflict with the Palestinians has obscured this progressive reality: it has pushed Israel's positive story from the headlines; and it has allowed Israel's longstanding enemies to build support for false analogies with some of the ugliest right-wing regimes imaginable - apartheid South Africa and even Nazi Germany itself.

Israeli speakers are shouted down in university campuses; otherwise left-wing union leaders demand wholesale boycotts of all Israeli produce; Israeli opposition politicians are afraid to come here for fear of arrest; leftish pop stars won't play concerts in Tel Aviv; and, bizarrely, an Israeli diplomat, Ishmael Khaldi, had to abandon an address at Edinburgh University after he was surrounded by protestors chanting "Nazi" and "boycott Israel". Khaldi is a Bedouin, Muslim Israeli citizen.

As of 2010, Israel had been condemned in 32 resolutions of the UN Human Rights Council, almost half of all resolutions passed since its creation.

In the decade of genocide in Darfur, unspeakable war crimes in Sri Lanka, and state-sponsored oppression of gay men and lesbians in a dozen African states, Israel remains the only country that the UN Human Rights Council has specifically condemned.

I mention all of this not to elicit sympathy or to play the victim card. But it is undeniable that today, if you are on the left it is presumed to be axiomatic to be anti-Israel.

How has this come to be? It's partly because there are two progressive principles that Israel is accused of denying the Palestinian people: one is their right to self-determination; the other is the general principle of "fairness", the sense that the Palestinians are not treated fairly by a powerful majority.

This belief is exacerbated by events. International sympathy for Israel rose when it was attacked by its neighbours in a series of attempted wars of annihilation. When bus bombs were exploding on a regular basis in Jerusalem, and gay bars were being targeted by suicide bombers in Tel Aviv, even hostile commentators were forced to admit that Israel was facing real problems.

And in response to this terror, to protect its people, Israel built a security barrier, which many didn't like, but has drastically limited the ability of suicide bombers to enter Israel, at least for now. And, facing security threats on the majority of its borders, Israel has been to war with Hezbollah in Lebanon, and has targeted Hamas in Gaza, who have been sending rockets into southern Israel on a daily basis since Israel unilaterally withdrew from the territory and Hamas took control of Gaza in a violent coup.

It was, I know, hard for people to watch what was happening in Lebanon and Gaza on their TV screens because innocent civilians were killed - as sadly happens in all wars.

Whereas Israel viewed these as wars of survival, support for Israel plummeted as a result. And just a few days ago we saw the terrible and gruesome murder of an Israeli family, and the pendulum swings back a little - until the next time.

And the fact is that because of Israel's understandably tough approach to security, including myriad check-points on the West Bank, as well as the Security Barrier, life for Palestinians can be really hard and restrictive, and that offends our sense of fairness.

But today I want to propose a new approach for progressives. Currently the dividing line is wrong. People are either categorised as pro-Israel or pro-Palestinian. This creates a pressure to support "your" side in a sectarian, loyalist sense.

As I have set out, it's because Israel embodies progressive values that I am a proud friend of Israel.

And yet I have observed a curious phenomenon: whenever I say something supportive of Israel I am almost always challenged to say something critical too. It's as if I have to buy permission to say something positive.

I'm regularly encouraged to be a "critical friend" by which is usually meant more criticism, less friendship.

My point is this: I want to work with all progressives - here, in Israel and the Palestinian territories - to build the confidence and trust that will be required to bring about a lasting agreement.

I will be critical of Israel when I need to be. But I call on my friends and colleagues who support the legitimate rights of the Palestinian people to cease the language of de-legitimisation; to end the comparisons with South Africa and Nazi Germany; to halt the demands for boycotts of Israeli produce and people; to put an end to the movement to sever academic ties; and to recognise Israel's strong and continuing adherence to the self-same progressive values that we fight for here at home.

It is not left wing or progressive to ally ones-self with those that seek Israel's destruction, or those who don't value one iota the type of society we strive for in this country. So I am appealing for all those who value peace and justice to support our values where we see them lived out, and to assist - not obstruct - those people working on the ground to resolve their conflict and build their progressive society.