The Hollywood Casino in Perryville, Maryland.(Photo by Doug Kapustin/For The Washington Post)

The measure has been drafted in response to a Washington Post story last week that reported that Maryland, one of only a few states where machines are not purchased by casino owners, is facing tens of millions of dollars in unanticipated costs.

Sen. Douglas J.J. Peters (D-Prince George’s) said the policy change will be considered as an amendment to a larger gambling bill that he is sponsoring. On Friday, the Senate Budget and Taxation Committee is expected to vote on that legislation, which would authorize a new casino in Prince George’s County and allow Las-Vegas style table games at all Maryland casinos.

Under the proposed amendment, casino owners would become responsible for procuring and paying for slot machines at their facilities. In exchange, the owners would be allowed to keep an additional 8 percent of proceeds.

“It came to our attention through the Washington Post article that this is a provision we should fix,” Peters said.

The state is paying an average of about $10,000 a slot machine per year to fill Maryland’s first three casinos, according to a Washington Post analysis. The cost of buying and leasing machines is more than double what officials estimated would be spent per machine in the coming year when lawmakers launched Maryland’s slots program in 2007.

At the current rate, the state could spend $50 million a year more than projected by the time all five planned casinos are open with nearly 12,000 machines.

Stephen Martino, director of the Maryland State Lottery Agency, said the policy on slot machine procurement was adopted by lawmakers in 2007 to bring “greater integrity and transparency” to the program.

Martino, who arrived in 2010, said that the added precaution probably wasn’t needed. That’s because slot machines in all Maryland casinos are connected to and monitored by a central computer system maintained by the state.

Peters’s larger bill faces tough odds in the remaining weeks of the General Assembly’s 90-day session. While it could pass the full Senate in coming days, House leaders have been lukewarm about the prospect of adding another casino before the five venues that were authorized by voters have all opened.

As written, the Peters bill would seek competitive bids for a sixth site from a swath in western Prince George’s that includes both National Harbor, the mixed-use development on the Potomac River, and Rosecroft Raceway, the recently opened horse track in Fort Washington.

Prince George’s County Rushern L. Baker III (D) has said he strongly prefers National Harbor, where he would like to see a billion-dollar casino.