For the kickoff of the 40th annual Chittenden County United Way fund-raising drive in Burlington, Vt., the sponsors considered themselves fortunate to have as guests Mayor Bernard Sanders of Burlington and Gov. Richard Snelling of Vermont.

But the charity workers heard the sort of things they wanted to hear from only one of their guests.

''I don't believe in charities,'' said Mayor Sanders, bringing a shocked silence to a packed hotel banquet room. The Mayor, who is a Socialist, went on to question the ''fundamental concepts on which charities are based'' and contended that government, rather than charity organizations, sho uld take over responsibilit y for social programs.

Governor Snelling sought to counter Mr. Sanders' remarks, saying: ''Charity is not a dirty word. We have discovered that you can't buy caring.''