For months, Prime Minister Keir Starmer’s Labour government has been under intense pressure from scores of its own members to demonstrate more robust support for Palestinians, especially in Gaza.

But a terrorist attack at a synagogue on Thursday in Manchester, England, which led to the deaths of two people during prayer services on Yom Kippur, exposed a competing political reality for Mr. Starmer: the growing anger among Jews in Britain who believe his government is doing far too little to protect them from hate and antisemitism.

The police have said the synagogue attack was carried out by Jihad al-Shamie, a British citizen of Syrian descent, and influenced by what they described as “extreme Islamist ideology.”

The anger at Mr. Starmer’s government was especially evident during a vigil on Friday for victims of the terrorist attack. David Lammy, the deputy prime minister, was booed off the stage by a rain-soaked crowd who angrily chanted, “Shame on you,” and loudly demanded that the Starmer government stop pro-Palestinian marches, saying they instill fear in Jewish residents.

Mr. Lammy expressed his condolences, but made little progress in calming the crowd. He pledged to “stand against all those who would minimize or coddle or obfuscate on anti-Jewish hate.” But he said nothing about banning the pro-Palestinian marches, even as members of the crowd continued to angrily call for it.

Tony Travers, a politics professor at the London School of Economics, called that demand “impossible,” but said it underscored the difficult position for Mr. Lammy, Mr. Starmer and other members of the government.