Viacom's MTV said on Wednesday it was standing by its controversial teen series "Skins" despite an exit of advertisers, a 50 percent slump in audience its and calls for a government pornography probe.

"Skins," an edgy new drama based on a British TV series of the same name, features a group of teens who dabble in drink, drugs and underage sex. Some of the largely unknown actors are as young as 15.

"The show is not canceled. The next episode is going ahead on Monday," an MTV spokeswoman told Reuters, responding to a media report the show was about to be axed.

Taco Bell, Subway, General Motors, Wrigley, Schick, H&R Block, Footlocker and L'Oreal have either pulled commercials from "Skins" or placed the series on a "do not buy" list in the last week.

Red Bull and skin care marketer Zeno Hot Spot ran ads in the latest episode on Monday, along with movie promotions from several Hollywood studios.

The move followed calls by a parents watchdog for a U.S. government investigation into possible violations of laws on the sexual exploitation of minors. U.S. laws ban the visual depiction of children or teens under 18 years of age involved in sexually explicit conduct.

Audiences for Monday's second episode dropped by half to 1.6 million U.S. viewers from the 3.3 million who watched the heavily promoted January 17 debut.

MTV said a fall-off in audiences for the second episode of a series are common and noted that the "Skins" audience was in line with that of other popular teen TV dramas "Gossip Girl" and "Vampire Diaries."

"'Skins' has earned the loyalty of fans across the globe for its thoughtful and honest portrayal of teen life today. An internationally acclaimed scripted drama, the show has been honored with a long list of prestigious awards. MTV stands by the U.S. adaptation of 'Skins' and the vision of its creator Bryan Elsley," MTV said in a statement.

MTV has declined to comment specifically on advertisers pulling out of the show but has said it has an "ongoing dialogue" with companies about the best fit for the various shows on the cable network.

The Hollywood Reporter on Tuesday cited an industry source as estimating that the loss of advertising could cost MTV $2 million an episode.

Elsley, meanwhile, said the show was a "very serious attempt to get to the root of young people's lives" and that the truth of how teens sometimes behave "can be a little painful to adults and parents."

Writing in the Huffington Post earlier this week, Elsley added: "Our approach is not careless. We've created a supportive and protective environment for everyone working on the show."