BOURNEMOUTH, OCT. 13 -- The motto of this week's Conservative Party conference here, emblazoned in bold, blue letters above the stage, was "The Strength to Succeed." But the underlying mood of Britain's ruling party was one of uncertainty and anxiety that even Prime Minister Margaret Thatcher's rousing closing speech could not dispel.

While Thatcher was exhorting the faithful to stand firm for her 11-year-old crusade for free enterprise, government statisticians back in London were issuing more bad economic news: Britain's annual inflation rate has now reached 10.9 percent, its highest level in eight years.

It was another signal that the economy is moving in the wrong direction and may be taking the party's hopes of winning a fourth straight term in office with it. For the Conservatives are up against a deadline -- by law, they must hold an election by the summer of 1992 and would much prefer to do so sometime next year. But first the economy must begin to show improvement, or else the party will be risking political suicide.

John Major, Thatcher's treasury secretary and the man she would most like to see succeed her sometime in the distant future, lowered interest rates by a point last week and tied the British pound to other currencies by joining the European Exchange Rate Mechanism. It was an attempt to swing the economy around in time for an early election, but analysts fear the threat of a deep recession remains strong, and Major has few other rabbits he can pull out of his hat.

"Opposition parties don't win elections; governments lose them," pollster Robert Worcester of Market & Opinion Research International said in an interview. "And the major issue is whether people feel optimistic about the economy. By that standard, this government is still in serious trouble."

Party conferences, like political conventions in the United States, have become stage-managed media events at which conflicts are concealed beneath a thick layer of adulation and sloganeering. But at the "fringe meetings" that took place away from the main conference center, disputes were on display this week that suggested the party is deeply divided and uneasy.

The biggest split was over Britain's role in Europe. Some of those considered prominent dissidents from Thatcher's cause -- including Deputy Prime Minister Geoffrey Howe and former Cabinet ministers Leon Brittan and Michael Heseltine -- insisted that for its own national interests Britain must become a more active participant in the move toward European economic and political union or risk being excluded.

"The next European train is about to leave, for a still undefined destination, but certainly in the direction of some form of economic and monetary union," Howe said. "Shall Britain be in the driver's cab this time? Or in the rear carriage?" But Thatcher loyalists made clear they see the move to join the exchange rate mechanism not as an opening step toward economic union, but as a final concession. Anything further would mean a profound loss of British sovereignty, they argued, and an empowering of an unelected European bureaucracy.

And the prime minister herself Friday reiterated her firm opposition to a single currency or a centralized bank for Europe. "Any such proposal involves a loss of sovereignty, which Parliament would not accept," she told the delegates to much applause.

But underlying the debate over Europe is a deeper sense of malaise and a fear that the party, after 11 years in power, is running out of ideological steam. "There used to be a certain brashness, an audacity, even a brazen commonness which gave Thatcherism not only its initial impetus but also its ability to go on defying the conventional political and economic wisdom," wrote columnist Ferdinand Mount in the Daily Telegraph, a newspaper that usually supports the party line. "The erosion of these qualities has left the Conservatives in a mild depression from which they badly need cheering up."

Thatcher tried hard, delivering an impassioned call to arms laced with biting humor and frequent, mocking attacks on the opposition Labor Party. She promised lower inflation, further income tax cuts "as soon as it's safe to do so," more privatization and better schools.

The speech may have cheered the faithful -- they responded with an eight-minute standing ovation -- but there was little in it that was new. And analysts said it was unlikely to have much impact on public opinion polls, which indicate that the Tories have narrowed the gap with Labor but remain anywhere from 8 to 12 points behind.

Perhaps more disturbing is a recent Gallup finding that only 26 percent of those surveyed believe Thatcher is doing a good job as prime minister. Only 18 percent said they would like to see her remain in office for another five years. Yet in recent days she has indicated to interviewers that she hopes to stay in office at least that long.

Loyalists believe that with interest rates falling, the party will pull even with Labor in the polls by Christmas and build a small but steady lead in the first half of 1991 as inflation begins to decline. After local government elections in early May, one senior adviser said, party leaders will analyze the results and decide whether to call a June national election.