An environmental activist charged with submitting phony bids for oil and gas drilling rights on public land in Utah crossed the line from lawful dissent into criminal conduct, a federal prosecutor told jurors on Tuesday.

Tim De Christopher "artificially inflated prices" for government mineral rights and "successfully sabotaged" an oil lease auction through his actions two years ago, Assistant U.S. Attorney Scott Romney said in opening statements at the felony trial.

If found guilty of fraud and violations of the U.S. Oil and Gas Leasing Reform Act, De Christopher, 29, faces a sentence of up to 10 years in federal prison and a $750,000 fine.

De Christopher has admitted posing as an energy developer when he took part in the public auction conducted in December 2008 by the federal Bureau of Land Management, an Interior Department agency.

The auction ended with De Christopher offering winning bids on 22,500 acres of land he said was valued at $1.7 million, most of it near Arches National Park and Canyonlands National Park, though he later acknowledged having neither the money nor the intention to make good on his purchase.

De Christopher said his bogus bid was intended to protest what he and other environmentalists see as a virtual government giveaway of valuable mineral rights under a poorly regulated program that leads to degradation of public lands.

Federal prosecutors, however, say De Christopher's act of civil disobedience deserves to be criminally punished.

"Mr. De Christopher chose to engage in a criminal form of activism," Romney said, adding that others protesting the 2008 lease sale "marched, chanted and made signs" outside the BLM office to register their dissent.

De Christopher, who remains free on his own recognizance, sat quietly through the first day of testimony dressed in a suit and tie. But he is expected to take the witness stand in his own defense on Wednesday.

Testimony began after the defense lawyer said he would hold his opening comments until the prosecution rested its case.

The first government witness, BLM employee Diane McComb, recounted that De Christopher arrived at the auction late.

"I asked him if he was a bidder, an observer or a member of the media. He told me he was a bidder," she testified. McComb said De Christopher filled out the necessary paperwork, then she handed him his bidding paddle.

Supporters of De Christopher have adopted his No. 70 paddle as a symbol for their cause.

His trial was expected to at least another day before the case goes to the jury for deliberations.

De Christopher says he rebuffed an opportunity to negotiate a plea deal with prosecutors, choosing instead to stand trial on principle.

"Part of the point of an act of civil disobedience is to take one's case before a jury of our peers, so they can decide whether or not my actions were justified," he told Reuters earlier in the week.

(Editing by Steve Gorman and Jerry Norton)

An environmental activist charged with submitting phony bids for oil and gas drilling rights on public land in Utah crossed the line from lawful dissent into criminal conduct, a federal prosecutor told jurors on Tuesday.

Tim De Christopher "artificially inflated prices" for government mineral rights and "successfully sabotaged" an oil lease auction through his actions two years ago, Assistant U.S. Attorney Scott Romney said in opening statements at the felony trial.

If found guilty of fraud and violations of the U.S. Oil and Gas Leasing Reform Act, De Christopher, 29, faces a sentence of up to 10 years in federal prison and a $750,000 fine.

De Christopher has admitted posing as an energy developer when he took part in the public auction conducted in December 2008 by the federal Bureau of Land Management, an Interior Department agency.

The auction ended with De Christopher offering winning bids on 22,500 acres of land he said was valued at $1.7 million, most of it near Arches National Park and Canyonlands National Park, though he later acknowledged having neither the money nor the intention to make good on his purchase.

De Christopher said his bogus bid was intended to protest what he and other environmentalists see as a virtual government giveaway of valuable mineral rights under a poorly regulated program that leads to degradation of public lands.

Federal prosecutors, however, say De Christopher's act of civil disobedience deserves to be criminally punished.

"Mr. De Christopher chose to engage in a criminal form of activism," Romney said, adding that others protesting the 2008 lease sale "marched, chanted and made signs" outside the BLM office to register their dissent.

De Christopher, who remains free on his own recognizance, sat quietly through the first day of testimony dressed in a suit and tie. But he is expected to take the witness stand in his own defense on Wednesday.

Testimony began after the defense lawyer said he would hold his opening comments until the prosecution rested its case.

The first government witness, BLM employee Diane McComb, recounted that De Christopher arrived at the auction late.

"I asked him if he was a bidder, an observer or a member of the media. He told me he was a bidder," she testified. McComb said De Christopher filled out the necessary paperwork, then she handed him his bidding paddle.

Supporters of De Christopher have adopted his No. 70 paddle as a symbol for their cause.

His trial was expected to at least another day before the case goes to the jury for deliberations.

De Christopher says he rebuffed an opportunity to negotiate a plea deal with prosecutors, choosing instead to stand trial on principle.

"Part of the point of an act of civil disobedience is to take one's case before a jury of our peers, so they can decide whether or not my actions were justified," he told Reuters earlier in the week.

(Editing by Steve Gorman and Jerry Norton)