A U.S. senator has urged the U.S. Department of Justice and the U.S. Federal Communications Commission to investigate whether Comcast is violating conditions imposed in its early 2011 merger with NBCUniversal.

Senator Al Franken, a Minnesota Democrat, questioned whether Comcast's recent decision to exempt its own Xfinity on demand service for the Microsoft Xbox 360 from its broadband data cap violates the merger conditions set by the DOJ.

"When the Obama administration signed off on Comcast's merger with NBCUniversal, it laid out a set of rules to prevent Comcast from squashing its competitors -- including popular cable alternatives -- and hurting consumers who have seen rapidly rising cable rates over the last several years," Franken said in a statement. "If Comcast is violating the administration's orders, it should face significant penalties so consumers know they can count on the administration to protect it from anticompetitive conduct that could mean higher bills."

Franken also raised concerns that Comcast's 250GB-per-month data cap will limit online video competition.

"I was very dismayed to hear that Sony recently announced that it is reconsidering launching an Internet TV service because it is concerned that Comcast will impose data caps on its competitors' programming," he wrote in a letter to the two agencies. "The conditions your agencies adopted were designed to foster innovation and encourage competitors like Sony to enter the online video market. If Comcast is able to impose restrictive data caps to the detriment of its competitors, I fear other companies like Sony will choose not to compete with Comcast."

Franken also objected to Comcast's refusal to put Bloomberg Television's channel near other business news channels in its cable lineup. The FCC ruled last week that Comcast should carry Bloomberg TV in the same channel "neighborhood" as other business news channels.

Comcast played down Franken's concerns. Comcast is fully complying with -- and "indeed exceeding" -- the merger conditions, said Sena Fitzmaurice, the company's vice president of government communications.

Comcast's On Demand service is "indisputably" part of the company's cable TV service and not subject to the FCC's net neutrality rules, Fitzmaurice added in an email.

"We are not aware of anyone who has taken a contrary view," she said. "When Comcast streams its own services over the open Internet, such streaming is subject to Comcast's broadband Internet data usage standards. But the Xfinity app for the X-Box does not stream content over the open Internet."

Grant Gross covers technology and telecom policy in the U.S. government for The IDG News Service. Follow Grant on Twitter at GrantGross. Grant's e-mail address is grant_gross@idg.com.