(Reuters) - New Civil Liberties Alliance, a conservative legal group, on Thursday filed what it said was the first lawsuit seeking to block Donald Trump's tariffs on Chinese imports, saying the U.S. president overstepped his authority.

The lawsuit, filed in federal court in Florida, alleges that Trump lacked the legal authority to impose the sweeping April 2 tariffs as well as duties authorized on February 1 under the International Emergency Economic Powers Act.

White House representatives did not immediately respond to an email seeking comment.

"By invoking emergency power to impose an across-the-board tariff on imports from China that the statute does not authorize, President Trump has misused that power, usurped Congress's right to control tariffs, and upset the Constitution's separation of powers," NCLA senior litigation counsel Andrew Morris said in a statement.

The lawsuit asks a judge to block implementation and enforcement of the tariffs and undo Trump's changes to the U.S. tariff schedule.