Some of Ronald Reagan's earliest conservative supporters yesterday celebrated the anniversary of his first year as president by charging that their one-time hero hasn't been conservative enough and has missed opportunities to move the country sharply to the right.

In a joint critique of the Reagan administration, a who's who of the nation's conservative political activists said the president has surrounded himself with political moderates, repeatedly has stumbled in foreign policy and is losing his chance to turn the country toward conservatism.

The critique, however, signed by 45 conservative leaders of both old-line and New Right organizations, treated Reagan gingerly. The group blamed most of the administration's problems on presidential advisers who it contends have not allowed the president to follow his natural conservative instincts.

"We speak in sorrow over this because of the lost opportunites," said Paul Weyrich, president of Coalitions for America. "President Reagan offered hope, but that has diminished. We are back to the old Republican way of doing business."

The group didn't give the president an overall rating, but Weyrich said he thought Reagan deserved no better than a "C or a C-minus" for carrying out his campaign pledges.

To regain the confidence of disgruntled conservatives, who not only have been the core of Reagan's political strength but are activists in both the Republican Party and conservative movements, the critique recommended Reagan bring more conservatives into his administration. It condemned any new tax increases, called for an "all-out effort" to cut social entitlement programs and for Reagan to rid the State Department of "relics of the Kissinger era and the Carter adminstration," and urged aid to "freedom seekers" in Angola, Afghanistan, Cuba, Nicaragua and Poland.

Administration foreign policy, it said, has been a "continued pursuit of the illusions of detente, restrained demeanor toward our communist opponents and cavalier treatment of our friends."

The critique was a compromise to satisfy both traditional conservative groups such as the American Conservative Union and more strident forces in the so-called New Right. Although there were no office-holders in the group, the signers represent the earliest core of Reagan's support in the conservative wing of the Republican Party, predating Reagan's unsuccessful 1976 presidential bid.

Like the activists in the liberal wing of the Democratic Party, the conservatives exert an influence on the Republican Party and its platform disproportionate to their numbers.

The critique was issued at a time of growing uneasiness over the Reagan administration among conservatives. The current issue of Human Events, a conservative weekly long outspoken in praise of Reagan, includes three biting attacks on the administration, one headlined "Reagan Revolution--Or Bush Rebellion?"

Many leaders of the New Right favored a far harsher critique: "I would have liked the guys to come down a lot harder," said Richard Viguerie, the New Right direct-mail expert. "There's a great deal of unhappiness with what's been happening at the grass roots level."

At a press conference following a day-long series of meetings, spokesmen for the conservative groups endorsing the critique insisted they were offering their criticisms as friends of the administration. They praised Reagan's political instincts, his budget and tax cuts and his ability as a communicator.

"However, there are things going on that we don't think Ronald Reagan agrees with," said Don Todd, executive director of the American Conservative Union.

Ron Godwin, executive vice president of the Moral Majority, urged Reagan to use the White House as a "bully pulpit on social issues," such as abortion and school prayer.