A major American donor for pro-Israel causes has cancelled his appearance at the AIPAC annual conference following a backlash against tweets falsely linking Muslim lawmakers Rashida Tlaib and Ilhan Omar to Hamas and the Muslim Brotherhood.

The two congresswomen "clash with American values", real estate mogul Adam Milstein said in a post on Monday, sparking outrage and accusations of anti-Muslim bigotry.

On Tuesday, Milstein said he will not be speaking at the American Israel Public Affairs Committee (AIPAC), to prevent the controversy from affecting the conference.

The Muslim Brotherhood is now part of Congress. New Reps. like @IlhanMN @RashidaTlaib are known as #AntiSemitic and Anti #Israel. Moreover, they both are representatives of #CAIR and #MuslimBrotherhood and their values clash with American values https://t.co/WsDcMie4z1 pic.twitter.com/M8MbOEAuob — Adam Milstein (@AdamMilstein) March 18, 2019

He was scheduled to moderate a panel on anti-Semitism at the AIPAC event next weekend.

However, Milstein did not retract or apologise for his original statement, which also claimed that Tlaib and Omar represent the Council on American Islamic Relations (CAIR), a US civil rights group often wrongly linked to the Muslim Brotherhood by conspiracy theorists and anti-Muslim bigots.

The Brotherhood, an Islamist political group active across the Middle East, is not designated as a terrorist group by the US State Department, but it is often vilified by right-wing commentators and politicians.

Still, Milstein dismissed accusations of Islamophobia on Tuesday, saying that he questioned the two lawmakers' values because he cherishes diversity.

"I believe that our country is stronger when people of all backgrounds and faiths are represented in public life," he said in a statement.

"It’s specifically because of these beliefs that I continue to speak out against CAIR as an organization, and against Representatives Omar and Tlaib who have long been associated with this extreme and patently intolerant group, which has a well-documented track record of spreading anti-Semitism and fundraising for the Hamas terrorist organization."

Normally I would say ‘racist obsessive nutcase troll’ but he happens to be a major figure and funder in the US pro-Israel lobby, including AIPAC. Believe it or not. https://t.co/1lvKNm6hUJ — Mehdi Hasan (@mehdirhasan) March 19, 2019

Ibrahim Hooper, a spokesman for CAIR, ridiculed the claim that Tlaib and Omar represent his organisation, saying that the two congresswomen, like all elected officials, only represent their constituents.

"We're an advocacy organisation, a civil rights organisation; we're used to being smeared by Islamophobes," Hooper told MEE. "But it takes it to another level when you accuse Muslim elected officials of dual loyalty merely because they're Muslim."

Milstien's remarks came after weeks of scrutiny and attacks on Omar who faced accusations of anti-Semitism for criticising AIPAC.

Speaking at an event in Washington last month, Omar said she wants to discuss the political influence that pushes for "allegiance to a foreign country", referring to the pro-Israel lobby.

The comments were interpreted by critics as an accusation of dual loyalty against Jewish-Americans.

Omar's supporters, however, rallied around her, arguing that the outrage is a drive to silence the debate around the Israeli-Palestinian conflict.

Hooper said the same kind of Islamophobia displayed by Milstein was also a factor in the attacks on Omar and Tlaib.

"I think it's clear that both congresswomen are coming under attack because they're Muslim and because they're women. We've seen that since they got elected, and even before."