Image by Wikimedia A 15th-century German artwork depicting the ritual killing of a Christian child. The “blood libel” was used for centuries to justify pogroms and other anti-Semitic acts.

The Palestinian organization that had organized Reps. Rashida Tlaib and Ilhan Omar’s planned delegation to Jerusalem and the West Bank once claimed that Jews put Christian blood in matzah, echoing a centuries-old anti-Semitic conspiracy theory.

Miftah, a not-for-profit run by longtime Palestinian peace negotiator Hanan Ashrawi, was forced to apologize in 2013 after publishing an article on its website criticizing then-President Barack Obama for hosting a Passover Seder at the White House, JTA reported at the time.

“Does Obama in fact know the relationship, for example, between ‘Passover’ and ‘Christian blood’..?! Or ‘Passover’ and ‘Jewish blood rituals?!’” read the post. “Much of the chatter and gossip about historical Jewish blood rituals in Europe are real and not fake as they claim; the Jews used the blood of Christians in the Jewish Passover.”

Accusations that Jews killed Christian children and used their blood to bake matzah was used for centuries to justify pogroms and other anti-Semitic acts.

After criticism from pro-Israel bloggers, Miftah at first called the allegations “a smear campaign” but eventually apologized and took down the article, JTA reported.

More Anti-Semitism reporting from The Forward

Tlaib and Omar’s trip was cancelled after Israel announced Thursday that they were invoking a law that refuses entry to supporters of the Boycott, Divestment and Sanctions (BDS) campaign against Israel.

The Israeli public broadcaster Kan reported that their itinerary involved meeting with several groups of Palestinian activists and charity workers, as well as American embassy officials and the Israeli anti-occupation organization B’Tselem.

Israel offered to allow Tlaib, who is Palestinian-American, into the West Bank to visit her grandmother as long as she didn’t use the opportunity to promote BDS. Tlaib declined on Friday.

Ashrawi, the leader of Miftah, claimed earlier this year that the Trump administration had turned down her request for a visa to visit relatives in the United States.

Aiden Pink is the deputy news editor of the Forward. Contact him at pink@forward.com or follow him on Twitter @aidenpink