Mark Smith, listed as a second secretary in the British Embassy in Ireland, wrote in a resignation letter to colleagues that was posted online that the Foreign Office “may be complicit in war crimes” by continuing to allow arms sales to Israel.

Mr Smith also said it was “deeply troubling” that the department had “disregarded” his concerns on the illegality of continued arms sales after he raised the issue internally.

He told the BBC Radio 4 Today programme: “For everybody watching their TV screens now, what we can see are appalling acts of violence perpetrated on civilians, on civilian property and so on.

“Most people I think watching that would think this is absolutely horrendous. For me personally, my profession, or former profession as of last week, was to advise the government on the legality of arms sales and when you look at what constitutes a war crime, it is actually quite clear, even from what you see on the TV, that the state of Israel is perpetrating war crimes in plain sight.”

Mr Smith said he was formerly the “lead author on the central assessment that governs the legality of the UK government’s arms sales to different countries” but he was not performing that role when he resigned last week.

“I wasn’t doing that job at the time that I resigned but I have worked in the Middle East directorate in almost all roles, on almost all countries at one time,” he told the BBC.

Review commissioned

A review into whether Israel is complying with international humanitarian law in Gaza was commissioned by David Lammy when he became Foreign Secretary and is ongoing.

A Foreign Office spokesman said: “This Government is committed to upholding international law.

“We have made clear that we will not export items if they might be used to commit or facilitate a serious violation of international humanitarian law.

“There is an ongoing review process to assess whether Israel is complying with international humanitarian law, which the Foreign Secretary initiated on day one in office. We will provide an update as soon as that review process has been completed.”

Israel has repeatedly denied it has committed war crimes in Gaza.

Mr Smith said that “anybody who has a kind of basic understanding of these things can see that there are war crimes being committed” and it was “not once, not twice, not a few times, but quite flagrantly and openly and regularly”.

Asked if he had raised that view during his time at the Foreign Office, Mr Smith said: “Yes. I raised it with the new Foreign
Secretary and I raised it at pretty much every level in the organisation.

“That is my duty and that would be quite normal I think for public servants. We are very used to upholding the law and so we would normally raise things internally that we might have a question over, particularly if we have a subject matter specialism as I do.”

Mr Smith would not be drawn on what the response to his comments was. “I am not at liberty to kind of go into detail about exactly how that internal process went. But I resigned from my role and I resigned because of this issue so you can put the pieces together, but suffice to say that any response was not satisfactory,” he said.