The current issue of the London Review of Books carries an important article by Seymour Hersh, based on extensive interviews with intelligence staff, in which he argues powerfully that the chemical weapons attacks in Syria, culminating in that of 21 August in which over 1,000 people died, were carried out not by the government but by the opposition. This is confirmed by analytical tests conducted by Porton Down which showed that the gas used in the attacks could not have come from Syrian government stocks.

Further, Hersh asserts, with evidence, that the gas attacks were carried out by Syrian opposition forces in concert with the Turkish government in order to throw blame on the Assad regime, thus crossing Obama's "red line" and triggering massive strikes by the US and its allies on Syrian government forces and the country's infrastructure. This is all the more concerning given the highly dubious nature of many of the opposition forces and their links to extremist factions – the danger, yet again, of our getting into bed with some very unpleasant "friends".

These are very serious claims and it is surprising that you still make the unqualified statement that "the Assad regime … was suspected of being responsible" (Chemical weapons body not ready to investigate Syrian attack claims, 12 April). At the very least, you should be reporting the doubts about who perpetrated these attacks, given that we could have been very nearly dragged into yet another Middle Eastern war on the back of bogus WMD allegations.

Dr Richard Carter

London

• Last year you published my letter about how every national newspaper had ignored Seymour Hersh's exposé of how the Obama administration had "cherry-picked intelligence to justify a strike against Assad" (Letters, 13 December). Confirming Marx's dictum that "history repeats itself, first as tragedy, then as farce", Hersh's new piece in the LRB has once again been blacked out by the press.

Ian Sinclair

London