Kaitlan Collins said she was excluded from a Rose Garden event after asking about Russian President Vladimir Putin and Trump's ex-lawyer.
Collins attended a photo opportunity with Trump and European Commission President Jean-Claude Juncker on Wednesday.
She was acting as the White House pool reporter – one of a rotating group of journalists, who will attend an event and write a report which all other networks can use.
This system allows networks to share the burden of covering the president.
Collins said she had tried to ask Trump questions about Russian President Vladimir Putin's postponed visit and recently released tapes documenting a conversation with lawyer Michael Cohen.
105retaliatory106not indicative of an open and free press.107wrongheaded
Traditional rival Fox News also attacked the ban.
122We stand in strong solidarity with CNN for the right to full access for our journalists as part of a free and unfettered press
Image credit: AFP/Getty Images