UPDATE 1-U.S. FCC's Pai, addressing internet rules, calls Twitter biased

(Recasts with comments about Twitter; adds quotes from Pai, background, support of additional FCC members)

WASHINGTON, Nov 28 (Reuters) - The chairman of the Federal Communications Commission, Ajit Pai, accused social media company Twitter Inc of being politically biased on Tuesday as he defended his plan to roll back rules intended to ensure a free and open internet.

Pai, a Republican named by President Donald Trump to head up the FCC, unveiled plans last week to scrap the 2015 landmark net neutrality rules, moving to give broadband service providers sweeping power over what content consumers can access.

"When it comes to an open internet, Twitter is part of the problem," Pai said. "The company has a viewpoint and uses that viewpoint to discriminate."

He pointed to Twitter's refusal to let Representative Marsha Blackburn, a Republican, advertise a campaign video with an anti-abortion message.

"To say the least, the company appears to have a double standard when it comes to suspending or de-verifying conservative users accounts as opposed to those of liberal users," Pai said.

Twitter did not immediately respond to a request for comment.

Twitter in October removed a campaign video by Blackburn, who announced she is running for the U.S. Senate, saying that a remark by Blackburn about opposing abortion was inflammatory. Twitter later reversed its decision.

Pai's criticism came a day after Twitter and a number of other internet-based companies - including AirBnb, Reddit, Shutterstock, Inc, Tumblr and Etsy - sent a letter urging the FCC to maintain the net neutrality rules.

Following Pai's remarks at an event organized by the libertarian-leaning R Street Institute, two other FCC commissioners said they would support his proposal when they vote on Dec. 14.

The proposed rollback has been seen as a victory for big internet service providers such as AT&T Inc, Comcast Corp and Verizon Communications Inc, which favored a repeal.

"So when you get past the wild accusations, fear mongering and hysteria, heres the boring bottom line," Pai said. "The plan to restore internet freedom would return us to the light touch, market-based approach under which the internet thrived." (Reporting by Diane Bartz and Ginger Gibson; Editing by Jonathan Oatis and Leslie Adler)