A set piece of the annual gathering of one of the most powerful political lobbies in Washington is the “roll call” of support in Congress for the American Israel Public Affairs Committee (Aipac).

Members of Congress are invited to stand one by one to be acknowledged for their support for Israel, or for Aipac’s hawkish brand of it. It typically takes half an hour as the names of around two-thirds of representatives and senators are called. It is intended to demonstrate that on one issue at least, the Jewish state, there are no partisan differences. It is also a reminder of the lock Aipac has long had on Congress with a menacing suggestion of the political risks of going against the lobby group.

But as Aipac’s convention opens, the carefully forged image of Democrats and Republicans at one on Israel has been battered by the furious reaction to Israeli prime minister Binyamin Netanyahu’s planned address to Congress on Tuesday, when he is expected to accuse Barack Obama of endangering the very existence of the Jewish state in negotiations with Iran over its nuclear programme.

Nearly 30 members have said they will not attend Netanyahu’s speech in protest at the extraordinary spectacle of Republicans inviting a foreign leader to Washington to denounce the president. They have described Netanyahu’s decision to speak as “sabotage” and “extremely dangerous”.

The dispute has also divided some of America’s most prominent Jewish organisations, with accusations flying of betrayal. But through it all Aipac has been all but silent as it struggles with the implications of the breach in the bipartisan wall as members of Congress with strong records of support for Israel challenge Netanyahu.

Some Democrats accuse Netanyahu and the Republican speaker of the House of Representatives, John Boehner, of using the speech to help the Israeli prime minister to bolster support ahead of this month’s general election, while the Republicans try to discredit Obama by undermining the president’s prerogatives on foreign policy.

Congressman Steve Cohen described the planned speech as “political theatre” that has “caused a breach between Democrats in Congress and Israel as well as the administrations of the United States and Israel”.

“While Americans and members of Congress may disagree on anything, even foreign policy, providing a forum of such immense prestige and power to the leader of another country who is opposing our nation’s foreign policy is beyond the pale,” he said.

It was a theme echoed by the president’s national security adviser, Susan Rice, on Wednesday as she warned that the speech is “destructive of the fabric of the relationship” between the US and Israel.

Few think the bedrock US support for Israel’s security, particularly military assistance, will be eroded. But Jeremy Ben-Ami of the liberal Washington lobby group J Street – which argues that the pro-Israel position would be to press Netanyahu to reach a negotiated settlement with the Palestinians – said the criticism in Congress is evidence of “a real disagreement about what is the best way forward to protect American interests, to protect Israeli interests”.

He said that increasingly among politicians and the American Jewish community the interests of Israel and the policies of Netanyahu are no longer regarded as one and the same.

Ben-Ami said that has opened the way for criticism from politicians who would once have remained silent. “All of these folks who say they don’t want to go to the speech or they’re upset about the speech, they’re friends of Israel. They hate not being able to say what they really think. You should be able to be a friend of Israel and say what you think,” he said.

“The silence at Aipac, the silence of some of the other groups, is testament to the fact that it’s going to be very difficult for them to maintain their traditional postures going forward given the arguments over policy.”

Aaron David Miller, who served six US secretaries of state as an adviser on Arab-Israeli negotiations, said the dispute creates problems for Aipac. “If you’re trying to build bipartisan support for Israel and you have an issue driving a wedge between Republicans and Democrats on Israel, then it complicates things,” he said. Aipac did not respond to requests for an interview.

The Israeli newspaper Haaretz reported that the speaker of the Knesset, Yuli Edelstein, was “stunned by the depth of the anger he found” over Netanyahu’s planned speech on a visit to the US Congress in February. Haaretz said Edelstein “met with Democratic congressmen who are sworn friends of Israel, but now feel betrayed by Israel’s prime minister”.

Critics include Senator Dick Durbin, a vocal supporter of Aipac who has addressed its annual conference and sponsored sanctions legislation against Iran.

Congresswoman Jan Schakowsky called the speech a “dangerous mistake”. “As a Jew, support for Israel is in my DNA,” she said. “I feel particularly anguished that the ill-advised invitation from Republican house speaker John Boehner has managed to threaten, in my view, both the security of Israel and the historic bipartisan support in the Congress.”

An Oregon congressman, Earl Blumenauer, accused Boehner and Netanyahu of conspiring to block a potential deal with Iran, saying it is “inappropriate” and “extremely dangerous”.

The speech has also divided influential Jewish organisations that have previously stood solidly behind Netanyahu over issues from settlement expansion to the wars with Hamas in Gaza. Abe Foxman, director of the Anti-Defamation League, a vigorous defender of Israel, called the speech “ill-advised”.

“This looks like a political challenge to the White House and/or a campaign effort in Israel,” he told the Jewish Telegraph Agency (JTA).

Morton Klein, director of the Zionist Organisation of America (ZOA), hit back by accusing Foxman of endangering Israel when it is under threat from a “terrorist regime” in Tehran. “How dare ADL’s Abe Foxman harm the US, Israel and the world’s efforts to fight these monstrous dangers by insulting the prime minister of the Jewish state and the US Congress by demanding Speaker Boehner rescind this important invitation,” he told the JTA.

The ZOA – along with other groups, such as the Republican Jewish Coalition, which are supported by a hawkish billionaire supporter of Netanyahu, Sheldon Adelson – called the boycott “anti-American, anti-patriotic”.

“We will, of course, be publicly condemning any Democrats who don’t show up for the speech—unless they have a doctor’s note,” he told Politico.