PORTLAND — The Oregon Lottery is beginning an aggressive campaign to upgrade video-lottery machines and bring in more players, even as research suggests that a relatively small group of problem gamblers supply a huge portion of lottery revenue.

The Oregonian newspaper reports that consultants found the biggest chunk of video-lottery players park in front of a machine and gamble alone until all their money is gone.

The lottery raises revenue for schools, parks, business development and other programs, and the lion’s share comes from video machines, which include both video poker and games similar to a slot machine. Critics say the government is fostering gambling addiction in order to pay its bills.

“It puts the government in the business of vice,” said Roger Humble, an addiction counselor who has treated more than 1,300 problem gamblers at the Bridgeway clinic in Salem. “We play them as suckers to help us pay our taxes.”

Lottery Director Larry Niswender defended the lottery’s practices and denied that the agency targets problem gamblers. He also disputed data showing that an outsize share of lottery revenue comes from a small group of players.

“I have a hard time believing there’s a very small number of people generating what is probably between $12 million to $14 million a week in revenue,” Niswender said. “It’s got to be a broad, diverse player base.”

A marketing plan details the agency’s strategy to recruit younger players. The first 3,000 of 12,000 replacement machines have been ordered and are likely to be installed next spring.

In the fiscal year that ended June 30, the lottery netted $856 million from all of its games: Powerball, Megabucks, scratch tickets, Keno and video machines. Eighty-six percent came from video. Oregon Lottery leaders plan to increase profits from video games by $10 million, or 3 percent, in fiscal 2014.

A November 2012 survey commissioned by the lottery shows that 48 percent of Oregon adults played at least one lottery game in the previous year. But just 10 percent played a video game, and only half of those played at least once a month.

At the same time, an estimated 2 to 4 percent of the population has some kind of gambling problem, most experts in the field agree. Oregon’s share is estimated to be between 35,000 and 80,000 people. Addiction counselors report that 75 to 90 percent who seek treatment for gambling problems play Oregon Lottery slot and poker machines.