In response to Mr Romney's decision, Matt Schlapp, chair of the American Conservative Union, wrote on Twitter: “BREAKING: The 'extreme conservative' and Junior Senator from the great state of Utah, @SenatorRomney is formally NOT invited to #CPAC2020.”
Despite Mr Romney’s efforts, the Republican-controlled Senate voted by 51-49 to block a push by Democrats to hear testimony from new witnesses, such as former national security adviser John Bolton.
In a manuscript for his upcoming book, the former national security advisor alleged that Mr Trump linked freezing military aid to Ukraine with forcing an investigation into Mr Biden.
With no new witnesses, it is almost certain the president, who has denied wrongdoing, will be acquitted next week.
Mr Romney has previously been a favourite of CPAC attendees and holds the record for winning the most CPAC straw polls for the most popular potential presidential candidate among conservative activists.
The senator has not yet commented on the decision and it is unclear if he was planning on attending the conference this year.
Michael Steele, a former chair of the Republican National Committee, described the decision to not invite the Republican senator to the conference as “embarrassing, stupid and juvenile”.
Soon after Mr Schlapp’s tweet, Mike Lee, Utah’s other Republican senator, tweeted in support of Mr Romney.
“Mitt Romney is a good friend and an excellent Senator. We have disagreed about a lot in this trial,” Mr Lee wrote.
“But he has my respect for the thoughtfulness, integrity, and guts he has shown throughout this process.”
Additional reporting by AP
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