We cannot sell arms to Israel and pretend to be shocked if they are used

The Foreign Secretary was emphatic three months ago. "It is extremely important that there should be the greatest certainty," he told the House of Commons, about what the Government would and would not allow to be exported to Israel.

That is the significance of the news that Britain is to export parts to the United States for the F16s that the US will then sell to the Israeli Defence Force. The position set out by Jack Straw in April seemed to have the merit of clarity, even if it did not satisfy those who wanted to see the sweeping symbolic condemnation of a full arms embargo on Israel.

The policy was that the Government would look at exports with a potentially military use and refuse permission for "anything that could be used for internal repression or for external aggression", in Mr Straw's words. This has been Labour's policy towards all countries since it marginally tightened up the guidelines on arms exports when it came to power in 1997, and since 1998 a common policy has been adopted by all the members of the European Union.

There does not seem to be much wriggle room there. It does not matter whether the occupation of the West Bank is defined as an internal matter for the Israeli state or a hostile action against a putative Palestinian state. Both Britain and the EU have made it clear that they are against it. Nor should it make any difference that the equipment is initially going to a third country when its ultimate destination is well known.

But the "certainty" of three months ago is now going to be modified. Mr Straw will set out new guidance on arms sales this week. So what has changed? According to a Downing Street spokeswoman, the new guidelines are needed "to take account of the new reality of multinational assembly lines for major defence contracts". We knew the global arms industries were dynamic and fast-changing, but this is a little too fast-moving for comfort. It looks too much like an adaptation of the words of an ethical foreign policy whenever they threaten to get in the way of British economic interests.

Usually, British governments have taken the right moral ground in their policy towards Israel. They support its right of self-defence and have no qualms about supplying arms for that purpose. But even Margaret Thatcher's government imposed a total arms embargo in 1982, as part of a European response to the invasion of Lebanon. That embargo was lifted in 1994, to be replaced by a version of the "case by case" policy we have now.

It might be argued that nothing the British government does or fails to do makes much difference, because the value of UK military exports to Israel is so small. So far, the only British contribution to the crushing of the Palestinian rebellion, with its inevitable civilian casualties, has been some 30-year-old Centurion tank chassis which were rebuilt as personnel carriers.

However, we do not urge on Mr Straw the idea of a complete embargo simply for the sake of a gesture. Certainly a full embargo would be largely symbolic, but symbolism and moral pressure are important tools of diplomacy. In order to be effective, though, moral condemnation must be sharpened by clarity.

Britain, and the EU, should condemn Israeli policy in the West Bank and should make that condemnation as emphatic as possible. Unless we are prepared to suffer some loss in our defence industries for the sake of it, our moral outrage is useless.