Faced with a staggering increase in families lining up for food each week, the United Way of Tri-County is launching a new fund-raising campaign as it tries to keep up with rising demand.

The regional agency, which runs food pantries in Framingham, Marlborough, and Clinton serving more than two dozen area communities, has started the Feed-A-Family for Fifty Campaign, which seeks $50 donations to provide households in need with a turkey dinner and fixings for Thanksgiving and the holiday season. It hopes to raise enough money to feed 3,000 families.