Prime Minister Margaret Thatcher offered the faithful of her Conservative Party today the promise of at least another two years of stringent fiscal policy, a strong defense and traditional social values to achieve what she described as her "vision" for Britain.

Despite hopes, and in some cases fears, that Thatcher would use the forum of her principal speech to the annual party conference here to announce major new initiatives, particularly to deal with record unemployment, she devoted herself to a restatement of the policies that swept the Conservatives to victory in 1979 and 1983.

"In the 6 1/2 years we have served the nation, much has been achieved," Thatcher said.

"The nation's output, the nation's investment, the nation's standard of living are at an all-time high.

"Inflation is down; . . . personal ownership is growing. Our overseas assets have multiplied more than sixfold in six years." Perhaps most important for the Conservatives, new trade union rules have limited the power of union "bosses" and brought strikes this year down to the lowest number in 50 years.

Thatcher's last address to the conference came only hours after she had narrowly escaped assassination during the 1984 session in Brighton. Five persons were killed and others severely wounded when a bomb, claimed by the Irish Republican Army, blew up the hotel where she was staying. For many Conservatives, her calm continuance of the conference's business reflected courage of a sort she asked them to display in maintaining her policies.

In terms similar to those used successfully by the Reagan administration in its 1984 reelection campaign, Thatcher described her original mandate -- that of "rolling back the frontiers of socialism and returning power to the people" -- as not yet fulfilled. Rather than pulling back now, Thatcher seemed to be saying, the only way to succeed is to press forward.

"We have set our sights high," she said. "But these goals are within our reach."

Unlike Reagan, however, Thatcher finds herself and her party in a midterm slump that political commentators feel they may not be able to surmount before the next elections, which must be held by the autumn of 1988.

Some senior party and government members have questioned whether more flexibility -- including increased government spending on job creation -- is needed in response to the current 13.8 percent unemployment and the party's flagging position in public opinion polls.

These concerns were largely muted this week during the carefully orchestrated conference.

The most startling exception was a speech last night in which Energy Secretary Peter Walker told the Tory Reform Group that "there must be no comfort in the fact that 87 percent are still at work." Such a "complacent attitude," he said, "is not just politically damaging, it is morally indefensible."

Walker, considered one of the chief moderates in the predominantly hard-line Cabinet, said that voters who accepted the 1983 Tory argument that some unpleasant medicine would be needed for economic recovery "will not accept the same excuses for a second time."

Other senior members of the government clearly considered Walker's remarks just short of treason to the party's efforts to present a calm and in-control face. In a television interview this morning, Chancellor of the Exchequer Nigel Lawson made an only slightly veiled suggestion that Walker, being a "man of honor," might consider resigning if he is incapable of supporting government policy.

Walker was conspicuously absent from the dais this afternoon during Thatcher's speech.

Thatcher said she was "only too painfully aware of the problem of unemployment." But while the government has provided training for unskilled youths and taken measures to encourage new businesses, she said, "there is one thing we will not do. We will not reflate."

The "vision" she offered Conservatives was of a Britain where jobs are created by booming private enterprise rather than state-owned industry, where every family owns its own home and car, "where law-abiding men and women go their way in tranquility with their children, knowing their neighborhood is safe and their country secure."

While her vision of Britain at home resembled the Reagan vision of life in the United States, Thatcher paid direct homage to Reagan in a brief section of her speech dealing with defense, in which she said that "the West could have no better nor braver champion."