Americans are being subjected to more sex, violence and profane language during the traditional, early-evening "family hour" of broadcast television viewing, a U.S. watchdog group said on Wednesday.

A study conducted by the non-profit Parents Television Council found that instances of violence during family-hour broadcast TV had increased by 52.4 percent since it conducted a similar study in 2001, while the amount of sexual content grew by 22.1 percent.

"In the past six years, the family hour has become even more hostile to children and families," the Parents Television Council said.

The family hour covers programs between 8 and 9 p.m. EDT Monday through Saturday and between 7 and 9 p.m. EDT on Sundays, the group said.

The Parents Television Council examined broadcast programs originally airing during three separate two-week periods of the 2006-2007 television season on the six major broadcast networks: Walt Disney Co's ABC, CBS Corp, News Corp's Fox; NBC, majority owned by General Electric; CW, a joint venture of CBS and Warner Bros.; and Fox's My Network TV.

Representatives of the networks were not immediately available for comment.

The group said it tallied 2,246 instances of violent, sexual and profane content in 180 hours of original programming on the networks, a number that amounted to one every 4.8 minutes.

It cited "adult-themed" shows that aired during the family hour, such as a Fox program called Bones, and Desire, which airs on My Network TV.

The Parents Television Council said broadcasters also were taking "graphic and explicit" programs originally run in later time slots and re-airing them during the family hour.

Only 10.6 percent of the 208 episodes in the study were free of any violent and sexual content and foul language, the Parents Television Council said.

The group tagged the Fox network as the "worst offender," saying it counted 20.78 instances of violent, sexual or profane content per hour. And it singled out Fox's American Dad as the most objectionable, with 52 instances per hour.

Parents Television Council said CW was the "cleanest" network overall, with 9.44 instances of objectionable content per hour. It said the only shows with no objectionable content were game shows and reality shows, such as NBC's Deal or No Deal.

The Parents Television Council said broadcasters and advertisers had undertaken efforts to "clean up" the family hour shortly after its 2001 study.

"Unfortunately that initial encouragement was short-lived," the group said.