By Diane Bartz

WASHINGTON A lawyer for the U.S. Justice Department pressed a Google executive on Wednesday about techniques the search and advertising giant used to push up online advertising prices in an allegedly unfair way.

Testifying at a once-in-a-generation antitrust trial in Washington where the United States has accused Google of abusing its dominance of search and some advertising, Google Vice President of Product Management Adam Juda said the company uses a formula, which includes the quality of an ad, to decide who wins auctions used to place advertising on websites.

Juda's testimony began on Tuesday and continued into Wednesday.

The Justice Department has accused Google of manipulating online auctions - a multibillion dollar industry dominated by Google - with these formulas to favor its own bottom line.

Justice Department attorney David Dahlquist asked Juda if he agreed with a document that Google had prepared for the European Union, which said that the company can "directly affect pricing through tunings of our auction mechanisms." Juda said he did not.

Pressed on if "tuning" can impact pricing, Juda said, "They can."

Juda said one thing that can be "tuned" is a rough formula that gives an ad a long-term value, or LTV, based on the bid given, the potential click-through rate or how many people will likely click on it and the quality of the advertisement and website associated with it.

Google's advertising business has been criticized by advertisers and website publishers for a lack of transparency, with both accusing Google of siphoning off too much revenue.

The testimony on advertising is a change from previous testimony that has focused on the billions of dollars that Google has spent to keep its search engine the default on smartphones and other devices.

(Reporting by Diane Bartz; Editing by Aurora Ellis)