Boris Johnson has accused Keir Starmer of “wanting Hamas to win” after the government announced it was suspending some arms sales to Israel.

The former prime minister hit out amid a mounting backlash over the decision, which foreign secretary David Lammy announced in the Commons on Monday.

Lammy said there was “a clear risk” of the UK-made weapons being used to break international humanitarian law in Gaza.

He said that around 30 arms exports licences to Israel are being suspended, out of a total of around 350.

Writing on X on Tuesday morning, Johnson said: “Hamas is still holding many innocent Jewish hostages while Israel tries to prevent a repeat of the 7th October massacre. Why are Lammy and Starmer abandoning Israel? Do they want Hamas to win?”

His criticism echoes that of Chief Rabbi Sir Ephraim Mervis, who said the government’s decision “beggars belief”.

Also writing on X, he said: “As Israel faces down the threat of Iran and its proxies, not just to its own people, but to all of us in the democratic west; this announcement feeds the falsehood that Israel is in breach of International Humanitarian Law, when in fact it is going to extraordinary lengths to uphold it.

“Sadly, this announcement will serve to encourage our shared enemies. It will not help to secure the release of the remaining 101 hostages, nor contribute to the peaceful future we wish and pray for, for all people in the region and beyond.”

Responding to Johnson’s comments on Radio 4′s Today programme, defence secretary John Healy said: “This is a government with a duty to the rule of law. This is not a decision about pleasing any side in this.

“When I spoke with the Israeli defence minister yesterday, I explained that we had a commitment to follow the rule of law, but I also made clear that the UK stands strong with Israel, and we are resolute in our determination to support their right to self-defence.”