Lord Prescott's description of Gaza as a "concentration camp" has been condemned on all sides of the political spectrum.
The former Deputy Prime Minister also wrote in his Sunday Mirror column that it was impossible not to view Israel's actions in Gaza as war crimes and compared the Israelis to Nazis.
"What happened to the Jewish people at the hands of the Nazis is appalling. But you would think those atrocities would give Israelis a unique sense of perspective and empathy with the victims of a ghetto," he wrote.
Labour Friends of Israel director Jennifer Gerber said Lord Prescott's comments were "provocative, factually ignorant and profoundly offensive," and urged him to retract.
Lord Prescott's comments were attacked in the House of Lords on Tuesday during a debate on antisemitism in Britain. Conservative peer Lord Leigh said: "It is unacceptable that many opt to use this conflict as a pretext for antisemitic prejudice, sometimes through the veneer of anti-Zionism by placards and rants in our own high streets, including the recent Mirror article."
He added: "Many Jews in this country feel that their security is threatened and their safety prejudiced."
Communities Minister Lord Ahmad said comparisons between the Holocaust and Gaza had no place in the protests.
Plans were announced on Monday to publish a parliamentary report into the upsurge of antisemitism. Labour MP John Mann, chair of the All-Party Parliamentary Group Against Antisemitism, said: "We must learn some lessons to ensure that Middle East tensions do not play out on the streets at home."
Former Foreign Office diplomat Lord Wright used the Lords debate to suggest people should "accept that much antisemitism is a reaction to the appalling Israeli treatment of its Arab neighbours".
In Wales, Plaid Cymru leader Leanne Wood called on First Minister Carwyn Jones to urge David Cameron to end the sale of weapons to Israel. Plaid Cymru MEP Jill Evans was among those who displayed a Palestinian flag at a 1,500-strong rally in Cardiff.
Elsewhere, Brazil and Ecuador recalled their ambassadors from Tel Aviv. Israeli Foreign Ministry spokesman Yigal Palmor said Brazil "remains a diplomatic dwarf".
In the United States grassroots activist group J Street has positioned itself more closely with mainstream Jewish organisations than during Israel's Cast Lead operation five years ago, supporting the IDF operation, but raising concern about civilians on both sides.
In Israel polls showed that Prime Minister Benjamin Netanyahu's high approval rates had slipped slightly, an indication of the frustration of the public at his reluctance to expand the operation. Eighty-seven per cent of the Israeli public supported the military action.
