The long-simmering disillusionment of the "New Right" with the Reagan administration broke into the open yesterday with the publication in conservative Digest of a series of attacks on President Reagan's appointees.

In a series of hard-hitting articles by the high priests of the New Right, the magazine, published by direct-mail expert Richard Viguerie, questions Reagan's commitment to conservative philosophy under headlines such as: "Ronald Reagan Should Try Reaganism," and "HUD's [Samuel] Pierce Delights Anti-Reagan Blacks."

The attacks start with an open letter to Reagan, which begins on the magazine's cover. "Your mandate for change is in danger of being subverted," writes Digest editor John Lofton. "Your personnel opration is being run by individuals who are politically naive and, worse still, individuals whose backgrounds reveal a hostility to most everything for which you have so strongly stood over the years."

The attacks continue for 23 pages, or almost half the magazine. The authors include some of the best-known leaders of the New Right: Terry Dolan of the National Conservative Political Action Committee, the Rev. Jerry Falwell of the Moral Majority, Paul Weyrich of the Committee for the Survival of a Free Congress, Howard E. Phillips of the Conservative Caucus and Phyllis Schlafly, the anti-ERA activist.