UPDATE 1-Top US Justice Dept antitrust official steps down

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WASHINGTON, Nov 7 (Reuters) - The top antitrust enforcer at the U.S. Justice Department, Thomas Barnett, will step down on Nov. 19, the Justice Department said on Friday.

Barnett, 46, has headed the antitrust division since June 2005, beginning in an acting capacity. He had spent a year as head of civil enforcement for the antitrust division.

During his tenure, Barnett came under criticism for allowing rivals that already dominated their industries to merge, such as satellite radio companies XM and Sirius (SIRI.O) and appliance makers Maytag and Whirlpool (WHR.N).

But he won praise for vigorously enforcing laws against corporations conspiring to raise prices.

"Under his leadership, the antitrust division has increased cartel enforcement to record levels with unprecedented fines and prison sentences," said Attorney General Michael Mukasey in a statement.

During Barnett's tenure, his division obtained $1.8 billion in criminal fines from 50 corporations and 91 individuals, the Justice Department said.

Price-fixers sentenced in the 2007 fiscal year were sentenced to an average of 31 months, a record, the department said.

There was no immediate word on Barnett's plans or who would replace him. (Reporting by Diane Bartz; Editing by Lisa Von Ahn and Brian Moss)