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Dozens gathered, chanting for a ceasefire, an end to the occupation and for the UK to stop arming Israel. They held handmade banners and Palestinian flags in the rain, and had come from across the capital.
Mr Starmer has defended Israel’s right to self-defence, after Hamas attacks on October 7 killed more than 1,300 Israelis with 200 taken hostage.
In earlier interviews he suggested that Israel had the “right” to withhold energy and water from the Palestinian territory. A number of his councillors have resigned over what they perceived as “horrifying” comments that he was “endorsing a war crime”.
Israel has cut Gaza's electricity and most of its water supply. It refused entry to humanitarian aid until Friday, and has repeatedly bombed the humanitarian corridor at the Rafah crossing on the border with Egypt.
More than 3,850 Palestinians have been killed by Israeli air strikes since the war began, according to the Gaza health ministry.
Labour has traditionally been the party for Palestine supporters. But the party is divided over its position on Israel and the Palestine issue. More than 30 MPs demanded a ceasefire this week, a sign that Mr Starmer could face a rebellion.
Mr Starmer sought to clarify his remarks about the siege on Friday, saying that food, fuel, water and medicines must urgently be allowed to pass into the territory as he acknowledged his earlier remarks caused “distress”.
He denied that he’d ever backed Israel withholding humanitarian aid from Gaza. “I was saying that Israel has the right to self-defence, and when I said that right I meant it was that right to self-defence. I was not saying that Israel had the right to cut off water, food, fuel or medicines,” he said. “On the contrary. For over a week now, I have been leading the charge calling for that humanitarian aid to come in.”
But this may be too little too late for Labour party supporters.
Eva Jay, who helped organise the protest, said there were events across the UK aimed at putting pressure on the Labour party. “We want to push Labour MPs in particular to depart from this consensus of complicity of genocide with Palestinians. A lot of Labour voters are in favour of Palestinian freedom and human rights,” she said.
Many of those gathered had been hopeful of a new Labour government after 13 years of Conservative rule, but were disappointed by Mr Starmer’s position on the war. “There was excitement around the possibility of a more socialist government in this country. More redistribution of wealth and more social justice. This is what the roots of Labour actually stood for,” Ms Jay said.
“We’re going to keep up the pressure,” she added.
Laura, a long-time Labour party supporter who attended the protest, welcomed Mr Starmer's clarifications, but said stronger condemnation of Israel was needed. “I’m glad he’s saying he does not support the cutting of water and electricity, I hope he will come out and publicly condemn that,” she told The National.
“I hope he will also say there must be an immediate ceasefire and adherence to international law, and that all forms of collective punishment are condemned by the UK,” she added.
She said she would not vote for Labour under Keir Starmer, “under [the party’s] current position”.
“I was really outraged and disappointed to see the Labour party not standing up for international law, human rights and calling for an immediate ceasefire,” she said.
“Using rhetoric that gave Israel green light to commit the atrocities its committing was deeply upsetting for me. It didn’t represent me in my views and how I feel we should be positioning ourselves in the UK,” she added.