British Prime Minister Rishi Sunak is facing growing political pressure to stop selling weapons to Israel after seven aid workers, including three British nationals, were killed by an Israeli air attack on Gaza.

Three opposition parties and some MPs in the governing Conservative Party said on Wednesday the British government should consider suspending arms sales.

The Liberal Democrats called for arms exports to Israel to be suspended, while the Scottish National Party also backed that move and said parliament should be recalled from its Easter break to discuss the crisis.

The main opposition Labour Party, which polls suggest will form the next government after elections expected later this year, said the government should suspend arms sales if lawyers had found Israel had broken international law.

“It’s important now that, that advice is published so that we can all be clear that if there has been a breach in international humanitarian law – and I must say that I do have very serious concerns – that arm sales are suspended,” said David Lammy, Labour’s foreign policy chief, told reporters.

Meanwhile, three former Supreme Court justices joined more than 600 members of the British legal profession in calling for the government to halt arms sales to Israel, saying it could make Britain complicit in genocide in Gaza.

“The provision of military assistance and material to Israel may render the UK complicit in genocide as well as serious breaches of International Humanitarian Law,” the judges and barristers said in a 17-page letter. “Customary international law recognises the concept of ‘aiding and assisting’ an international wrongful act.”

The attack on the convoy of people working for aid group World Central Kitchen (WCK) killed citizens of Australia, the UK and Poland as well as a Palestinian and a dual citizen of the US and Canada. Israeli Prime Minister Benjamin Netanyahu said that the strike was tragic and unintended, and the Israeli military pledged an independent inquiry.

WCK said its staff were travelling in two armoured cars emblazoned with the charity’s logo and another vehicle, and had coordinated their movements with the Israeli military.

Several of Israel’s key allies also expressed outrage at the deaths and called for an independent investigation into the attack.