Britain’s envoy to the United Nations has provided a further legal justification for the RAF killing of Islamic State (Isis) fighters in Syria, declaring that it was on behalf of the “collective self-defence of Iraq”.

The new explanation, which was not disclosed to MPs at Westminster when David Cameron first told MPs about the killings, prompted Jeremy Corbyn to accuse the prime minister of facing “two ways” on Syria.

David Davis, the former shadow home secretary, said the government should consult MPs on the grounds that the letter by Matthew Rycroft, the UK’s permanent representative to the UN in New York, appeared to show a “material change of strategy”.

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The letter cites the justification given by Downing Street for the killing, referring to Article 51 of the UN charter: “This airstrike was a necessary and proportionate exercise of the individual right of self-defence of the United Kingdom.”

Rycroft’s letter goes on to state: “As reported in our letter of 25 November 2014, Isil [Isis] is engaged in an ongoing armed attack against Iraq, and therefore action against Isil in Syria is lawful in the collective self-defence of Iraq.”

The prime minister made no mention of defending Iraq when he told MPs on London that an RAF Reaper drone had killed two British jihadis, Reyaad Khan and Ruhul Amin, in the Syrian city of Raqqa, in a strike on 21 August.

Philip Hammond, the foreign secretary, did tell MPs on the foreign affairs select committee on Wednesday that an extension of British involvement in the regular coalition air strikes against Isis targets in Iraq to Syria would be justified on the grounds that it would help defend Iraq. The remarks by Hammond were seen as “pitch rolling” – the phrase to describe the preparation of opinion for a change in strategy – for a parliamentary vote on whether to join the coalition airstrikes over Syria.

The government said it had no need to consult parliament on the drone strike which killed Khan last month on the grounds that it was an emergency act of self defence to prevent him plotting terror attacks. Jeremy Corbyn, the frontrunner for the Labour leadership, said the prime minister’s failure to mention the extra justification of defending Iraq raised important questions about whether parliament had been properly consulted.

Corbyn said: “The government appears to have used an additional and entirely separate justification for this covert strike in their letter to the UN, which was not mentioned in the prime minister’s statement to parliament. Why did the government cite the defence of Iraq when justifying this strike to the UN, but not when doing so to parliament?

“Is it because parliament previously voted against action in Syria, making this justification at odds with the will of the Commons? The prime minister cannot face two ways on this issue – he needs to urgently explain this discrepancy.”

David Davis, the former shadow home secretary, said the government should consult MPs over its new justification. Davis said: “In a fluid situation like this the inclination of the House of Commons is to give the government the benefit of the doubt. But you get to a point where they are going to need to come back and actually get approval. I think we are approaching that point: put the policy to the house in a vote.

“There was a vote about Syria [in August 2013], then there was a vote about Iraq [in September 2014] and they explicitly excluded Syria because they were concerned about not winning the second vote. Therefore that implies this is a material change of strategy and such it becomes the norm that they should come back to the house. A single attack is perfectly legitimate so long as it is validated by the facts. If it is going to be a policy change they do need to come back to the house.

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“This letter would imply that if they are going to continue with drone strikes then they should come back to parliament to validate that strategy. This is such a new excursion for us – explicitly killing named people – that they should come back to parliament.”

The letter dated 7 September – made public for the first time on Thursday – was obtained by the London-based human rights group Reprieve, which has questioned the legality of the drone strike. Human rights groups said that providing two alternative legal arguments as cover for military action against Isis fighters in Syria implies a lack of self-confidence among British officials. The UN, it was claimed, might not be convinced that an attack on the UK, supposedly organised by Reyaad Khan, had been imminent, and the additional justification had therefore been added.

Jennifer Gibson, a lawyer at the UK civil rights group Reprieve, said: “David Cameron needs urgently to answer questions about whether there was genuinely an imminent threat to the UK or is this an expansion of the war against Isis without parliamentary approval? This argument was never raised in parliament. It can’t be both explanations.”

Philippe Sands QC, professor of international law at University College London, said: “The wording of the [Rycroft] letter is ambiguous but it appears to posit two alternative justifications. The first is the self-defence of the United Kingdom, the second is collective self-defence in support of Iraq. The latter is an entirely different justification as a legal matter [for carrying out attacks in Syria].”

Corbyn criticised Cameron over the airstrike in Syria, saying he would not have authorised it. Speaking on ITV News, Corbyn said: “The prime minister has some very difficult questions to answer about the legality of what he did. I’m unclear as to the point of killing the individual [Reyaad Khan] by this drone attack.”

Rycroft’s personal involvement will also raise eyebrows. He was Tony Blair’s private secretary at the time of the 2003 invasion of Iraq.



His name was on a key memo revealing that Britain and the US were planning five months before the invasion to take action against Saddam Hussein without a second UN resolution.

By coincidence, Iain Macleod, legal adviser at the Foreign Office, was also legal counsellor at the UK mission to the UN in New York in the run up to the Iraq invasion.