WASHINGTON — Speaker John A. Boehner’s effort to pass fallback legislation to avert a fiscal crisis in less than two weeks collapsed Thursday night in an embarrassing defeat after conservative Republicans refused to support legislation that would allow taxes to rise on the most affluent households in the country.

House Republican leaders abruptly canceled a vote on the bill after they failed to rally enough votes for passage in an emergency meeting about 8 p.m. Within minutes, dejected Republicans filed out of the basement meeting room and declared there would be no votes to avert the “fiscal cliff” until after Christmas. With his “Plan B” all but dead, the speaker was left with the choice to find a new Republican way forward or to try to get a broad deficit reduction deal with President Obama that could win passage with Republican and Democratic votes.

What he could not do was blame Democrats for failing to take up legislation he could not even get through his own membership in the House.

“The House did not take up the tax measure today because it did not have sufficient support from our members to pass,” Mr. Boehner said in a statement that said responsibility for a solution now fell to the White House and Senator Harry Reid, Democrat of Nevada, the majority leader. “Now it is up to the president to work with Senator Reid on legislation to avert the fiscal cliff.”