(Updates with details)

* Targets "gateway sexual activities" like touching genitals

* Critics fear limitations will hamper safe sex education

* Tennessee's sex ed law fodder for comedians

By Tim Ghianni

NASHVILLE, Tenn, May 11 (Reuters) - Tennessee teachers can no longer condone so-called "gateway sexual activity" such as touching genitals under a new law that critics say is too vague and could hamper discussion about safe sexual behavior.

Governor Bill Haslam's office Friday confirmed that he had signed the bill, which stirred up controversy nationwide and even was lampooned by comedian Stephen Colbert.

"Kissing and hugging are the last stop before reaching Groin Central Station, so it's important to ban all the things that lead to the things that lead to sex," he said on the "Colbert Report" television show.

But proponents say the new law helps define the existing abstinence-only sex-education policy.

Under the law, Tennessee teachers could be disciplined and speakers from outside groups like Planned Parenthood could face fines of up to $500 for promoting or condoning "gateway sexual activities."

David Fowler, president of the Family Action Council of Tennessee, which pushed the bill, said it does not ban kissing or holding hands from discussion in sex ed classes. But he said it addresses the touching of certain "gateway body parts," including genitals, buttocks, breasts and the inner thigh.

It is unclear from the bill's wording whether Tennessee teachers could promote masturbation.

The bill sailed through the legislative session, passing the Senate 28-1 and the House 68-23.

Opponents, which include Planned Parenthood of Middle and East Tennessee and the state teachers' union, say that before they can begin fighting the new law, they have to be able to figure it out. They worry that discussion of sexual behavior could be interpreted as condoning it.

"The very ambiguous language in this bill certainly puts teachers in a very difficult situation" when it comes to knowing what to teach, said Jerry Winters, spokesman for the Tennessee Education Association.

Fowler said the new law was authored in part because of incidents in which teachers were instructing about alternate sexual practices as ways to have gratification without risking pregnancy, according to Fowler.

He said one such incident involved a Nashville high school teacher who was encouraging girls to give boys oral sex in order to get a condom on them.

Fowler also pointed to a Planned Parenthood-organized program at a school in Knoxville, where students were directed to a web site "that actually lists as possible methods of birth control things like oral sex and anal sex play that I think most Tennesseans would find inappropriate."

Lyndsey Godwin, manager of education and training for Planned Parenthood, said the idea that her group was encouraging such behavior was "utterly false." She said that while Planned Parenthood educators may answer a student's question by agreeing that anal and oral sex don't lead to pregnancy, they also emphasize the disease risks.

Godwin said Planned Parenthood supports the state's abstinence-centered policy, but the reality is not everyone can be abstinent. She said that being able to address issues of condom use, contraception and answer questions about sexual behaviors to educate students are essential to her group's role.

Winters of the Tennessee Education Association said that already existing sex education policy was "quite adequate."

"It does focus on abstinence, but in this modern world to say that 'just say no' is the answer to teenage pregnancy is putting your head in the sand," Winters said. (Reporting By Tim Ghianni; Editing by Mary Wisniewski and Lisa Shumaker)