BOSTON — A group of four freshman Democratic lawmakers, backed by more than a dozen others, issued a statement Thursday to "demand" that Congress ban assault weapons and implement universal background checks for firearm purchases across the United States.

Reps. Lindsay Sabadosa of Northampton, Nika Elugardo of Jamaica Plain, Tami Gouveia of Acton and Maria Robinson of Framingham issued the statement on the heels of two mass shootings last weekend to "fully denounce the white supremacist rhetoric that continues to be perpetuated and normalized in our country and that is one of the root causes of these acts of violence."

"We acknowledge that racist, homophobic, xenophobic, nationalistic, and militaristic statements by people in positions of power have continued to bolster white domestic terrorism and the never-ending cycle of violence in our country, particularly when coupled with weak federal gun laws," the group wrote in the statement. "Therefore, we demand that our federal government act immediately to ban assault weapons and institute universal background checks with no loopholes. While we too offer our 'thoughts and prayers,' we acknowledge our own complicity in white supremacy culture and the need to take real and immediate action to stop gun violence and discriminatory rhetoric that plagues our country."

Seventeen other lawmakers, all Democrats, signed onto the statement: Sens. Michael Barrett, Jamie Eldridge, Patricia Jehlen, Barry Finegold, Edward Kennedy, Jason Lewis and Joan Lovely, and Reps. Jim Hawkins, David LeBoeuf, Jack Lewis, Christina Minicucci, Liz Miranda, Tram Nguyen, Denise Provost, Ted Speliotis, RoseLee Vincent and Bud Williams.

Massachusetts already has a ban on assault weapons, and Attorney General Maura Healey in recent years has stepped up enforcement of the prohibition on copycat assault weapons.