By Douwe Miedema

WASHINGTON (Reuters) - A Tennessee man was charged with attempting to extort $1 million during last year's election by threatening to release former Republican presidential candidate Mitt Romney's tax returns that he falsely claimed he had stolen, the Department of Justice said on Wednesday.

Michael Mancil Brown, 34, was indicted on six counts of wire fraud and six counts of extortion in U.S. District Court in Tennessee, the agency said.

Romney's taxes were a hot political issue last year during the presidential campaign because he refused to release several years of his personal tax returns.

Brown was charged with demanding $1 million worth of the digital currency Bitcoin to hand over tax documents that he said he obtained by gaining access to the computers of accounting firm PricewaterhouseCoopers.

Brown sent a letter to the offices of PricewaterhouseCoopers in August 2012 to demand the money and invited others wanting the tax documents to transfer $1 million to another Bitcoin account, according to the indictment.

The indictment alleges that Brown delivered similar letters to the Democratic and Republican parties.

(Reporting by Douwe Miedema; Editing by Cynthia Osterman)