Supporters of a bill granting in-state tuition rates to some undocumented immigrants filed a lawsuit Monday seeking to overturn an effort to put the issue on the 2012 ballot.

Casa De Maryland, in a statement released this morning, said the lawsuit was based on "illegalities discovered in the signatures submitted to and incorrectly validated by the Board as well as the grounds for relief."

A copy of the suit was not immediately available.

The lawsuit was filed by Casa De Maryland, SEIU Local 1199 and the Maryland State Education.

Del. Pat McDonough, a Middle River Republican and outspoken opponent of the tuition bill, said the lawsuit was meaningless.

"It's a desperation move," McDonough said. "Obviously it doesn't have much merit since the ACLU doesn't want to participate."

The challenge to the referendum effort was not unexpected.

In June, the American Civil Liberties Union sent a letter to the Maryland State Board of Elections challenging the electronic petition form used by opponents of the bill.

"Every system in the country is subject to fraud," McDonough said of the ACLU complaint and the lawsuit. "You can't just say something is subject to fraud.

"You must prove that fraud occurred and you have to prove that it has an impact on the outcome [of the referendum drive]," he said. "I don't think that's possible."