The Islamic Human Rights Commission (IHRC) wrote to 460 town halls and educational centers asking them to boycott the UK's Holocaust Memorial Day.
The IHRC, which British media has linked to Iran, said it was "morally unacceptable" that Gaza was not considered a "genocide" alongside the Holocaust.
The Holocaust Memorial Day this year - on January 27 - will commemorate 80 years since the liberation of Auschwitz.
IHRC also wrote a letter to the Holocaust Memorial Day Trust itself, imploring the body to include Gaza on the list of genocides.
The letter quotes the Holocaust Memorial Day's website, which states the aim of the day is to remember the six million Jews murdered during the Holocaust, as well as victims of recent genocides in "Cambodia, Rwanda, Bosnia, and Darfur.”
IHRC said that the failure to include Gaza in commemorations undermines the aim of marking the Holocaust, which is to prevent further genocides from occurring.
"Failure to recognize Gaza as a site of genocide is to remain silent in the face of profound injustice," it said.
"We urge supporters to request HMD organizers to acknowledge the genocide in Gaza in their 2025 commemoration."
It added that if the organizers refuse, supporters should "publicize the event organizer’s refusal to recognize all genocides, including that of the Palestinians in Gaza" and "organize a boycott of their event until they commit to opposing and condemning all genocides universally."
The chief executive of the Holocaust Educational Trust, Karen Pollock, told The Telegraph that the IHRC’s call to boycott the day was “shocking and disgraceful."
“This is a cynical attempt to denigrate and undermine the memory of the Holocaust by drawing false parallels between the Holocaust – a unique and unprecedented episode in history – and unrelated current events," she added.
“It is vital that commemorations maintain their focus on the Holocaust, that Jewish victims are properly honored, and that the central role of antisemitism in this genocide is unequivocally recognized," Pollock continued.
Investigation into IHRC
In an independent report carried out in 2023, the Prevent counter-terror strategy called the IHRC an "Islamist group ideologically aligned with the Iranian regime."
It also stated that several of IHRC's leaders have shown support for violent jihad and expressed a desire to eradicate "Zionists."
At the time, a spokesman for the group called the report "Islamophobic."
At a vigil for IRGC officer Qassem Soleimani in 2020, Massoud Shadjareh, the chair of IHRC, said, "We aspire to become like him."
Speaking on the boycott, Shadjareh said, “We have suspected for a long time that HMD promotes exceptionalization of genocide through the Nazi Holocaust. Any failure to include the actual genocide that is unfolding so graphically in our own time gives the lie to the slogan “Never Again,” exposing it as a political device to promote one genocide over all others. Civil society cannot allow the Gaza genocide to be legitimized by the misappropriation of the Nazi Holocaust”.