NEW YORK — In a counter-punch to the world's biggest online hangout, a small Web company called Power.com has sued Facebook, saying it doesn't follow its own policy of giving users control over their content.

Power lets users simultaneously access several social networks, including MySpace and Twitter. But Facebook isn't among them because the site has blocked Power. Last year it sued Power over the practice.

In that lawsuit, Facebook accused Power of copyright and trademark violations and said the company gains unauthorized access to Facebook's computer network when it asks users for their Facebook login and password information. This, Facebook says, violates its members' privacy and security.

San Francisco-based Power filed a countersuit Friday in U.S. District Court in San Jose, Calif. Power claims that Facebook improperly restricts its users' access to their private information when it prevents them from accessing it through a third party like Power.

In a statement Friday, Facebook said called the lawsuit "without merit" and said it plans to fight Power aggressively.

"We have made numerous attempts to work with Power.com but, after making commitments to comply with our policies, they continued to put Facebook user data at risk," Facebook said.