From Lord Thomas of Swynnerton.

Sir, Richard Haass ("It is too soon to talk of attacks against Iran", April 12) made a strong case for not taking any kind of armed action against Iran because of its apparent commitment to manufacture nuclear weapons. All the same, diplomacy, even economic diplomacy, would be more effective if we were able to insist that we - the west, that is - were genuinely concerned not only about the "spread" of nuclear weapons but also about their existence. Could we not perhaps link our desire to prevent the development of an Iranian nuclear weapon with a new version of traditional United Nations policies such as in the past all the main parties in this country supported?