Senator Scott Brown demanded Friday that his Democratic rival, Elizabeth Warren, reimburse taxpayers for the $276,000 that the state spent to mail thousands of voter registration forms to welfare recipients.

Brown, a Republican, has argued the mailing to nearly 500,000 welfare recipients was a partisan plot to boost Warren’s campaign, since it was spurred by a lawsuit filed by Demos, a liberal group that is chaired by Warren’s daughter.

State officials have said they agreed to the mailing to ensure they were in compliance with the National Voter Registration Act, the federal law that requires welfare offices to provide recipients with voter registration materials. Demos, the group that brought the lawsuit, has said Warren’s daughter played no role in the suit, and pointed out they have filed similar lawsuits in eight other states.

Brown made his demand in a statement issued by his campaign.

“It’s been disturbing for a lot of people to learn that the state’s welfare department undertook an unprecedented voter registration drive at the behest of Elizabeth Warren’s daughter and the organization she represents,” he said. “It is clear that this was done to aid Elizabeth Warren’s Senate campaign. Professor Warren has more than $13 million dollars in her campaign account, and if she wants to mail every welfare recipient a voter registration form, she should do so at her own expense, not taxpayers’. She should immediately reimburse the state for the cost of this mailing and stop playing politics with the taxpayers’ money.”

The Warren campaign had no immediate response this morning.