White House chief strategist Steve Bannon "fat shamed" press secretary Sean Spicer, Chelsea Clinton has said.
The former first daughter criticised Mr Bannon on Twitter, saying the White House was "using fat shaming to justify increased opacity".
Mr Bannon told The Atlantic in a text message a day earlier the reason News briefings had been held off-camera was because "Sean got fatter".
Mr Bannon did not respond to follow-up questions nor elaborate on his remarks.
The White House has been holding a series of off-camera briefings in place of the traditional daily media events.
The Trump administration has frustrated White House reporters by also restricting the use of audio and video during the briefings.
Ms Clinton, the daughter of former President Bill Clinton and 2016 Democratic presidential candidate Hillary Clinton, retweeted British author Brian Klaas, who called Mr Bannon's excuse "pathetic and undemocratic".Image copyright Twitter
But some conservatives were quick to defend Mr Bannon, describing his response as harmless fun.
White House reporter Charlie Spiering of Breitbart News, which Mr Bannon previously led,
It’s a joke people… https://t.co/2mMNcX7GHY— Charlie Spiering (@charliespiering) June 20, 2017
Jim Hanson, president of a national security group,
a "PR-managed response from the humour-impaired left".
PR-managed response from the humor-impaired left— Jim Hanson (@Uncle_Jimbo) June 20, 2017
It was a joke https://t.co/EeUucx2P91
Ms Clinton fired back at both men, noting she didn't take fat-shaming lightly.Image copyright Twitter
The Twitter spat comes as US media reported the White House is considering moving Mr Spicer to a more senior communications role.
Communications director Mike Dubke stepped down earlier this month.