A patient advocacy group sued the federal government Wednesday to try to force U.S. health agencies to acknowledge that marijuana has merit as a medicine.

The lawsuit by Americans for Safe Access follows a two-year effort to reverse what it calls a "misinformation campaign" by U.S. health agencies.

Americans for Safe Access is suing under the Data Quality Act, a little-known statute that lets citizens challenge the accuracy of government-disseminated information.

The Oakland-based group filed a petition in October 2004 asking the United States to reverse its staunch opposition to pot as medicine. After months of delays, the government rejected the petition.