ALBANY — The US Justice Department yesterday said it would not challenge a plan by New York Republicans to add a seat to the state Senate through redistricting.

But a lawsuit backed by Democratic legislators challenging the plan is still being considered by the state’s top appeals court.

Washington’s decision removed a potential obstacle from a plan signed into law by Gov. Cuomo but criticized by good-government groups. They charge that it continues using redistricting to protect a majority’s power by contorting districts until a certain party’s voters dominate.

Republicans hold a 32-30 majority in the state Senate.