LONDON (AP) _ With a U-turn on coal mine closures, Prime Minister John Major has bought a costly political reprieve.

But the road ahead looks even rockier.

Major supporters roared approval Wednesday night when the government, in a 320-307 House of Commons vote, defeated an opposition motion opposing the closure of 31 money-losing mines.

The government scraped by only because Major had shelved most of the program himself to avert rebellion in his Conservative Party.

He promised to think again on the fate of the mines, which were marked for closure just a week ago, and won approval of the review by a vote of 305-302.

Major faces another vote in three months, when the government is scheduled to announce its promised review.

Toppling the record of his predecessor, Margaret Thatcher, Major is now the most unpopular British leader since opinion polling began in the 1940s, according to a poll published today.

Struggling from this base to reassert political credibility and to chart a new economic strategy, he faces confrontations over government pay raises and over ratification of a treaty on closer European union.

As with the coal debacle, his authority is threatened by Conservative dissidents rather than by the Labor Party, which has lost the last four elections.

Broadly, Major's aides blame his predicament on the worldwide economic slowdown. The mood is particularly resentful in Britain because the recession is nearly 3 years old and the Conservatives won a new five-year term in April on promises of recovery.

Like President Bush, Major finds the public turning against him after promises of economic recovery gave way to a deepening recession.

''I used to call myself a true-blue Conservative, but now I'm only a middling Conservative,'' said Jacqueline Aslan, 38, who feels stuck in her job as a travel agent because new opportunities have vanished.

Major ''doesn't appear to be a tough enough character to take charge.''

''We're losing heart with the Conservatives now,'' said Barry Charman, who runs an office-cleaning business in Boreham, north of London. ''I just don't know what's going wrong.''

Like most small businessmen, Charman voted Conservative in the last election in April.

Major's slim 21-seat majority in the 651-member Commons has left him vulnerable to rebellion - in contrast to the authoritarian Mrs. Thatcher, who had a near 100-seat majority.

To square the circle of holding 1993-94 government spending to a total of $393.6 billion without deepening the recession, Major on Tuesday announced a squeeze on public sector pay - with raises of no more than 2 percent, if salaries increase at all.

To do so means taking on lobbies such as nurses. Their pull with Conservative rank-and-file and middle-class voters can be as emotive as the salt-of-the-earth appeal of the miners, who staged a big demonstration in London on Wednesday.

And after Major's debacles and backdowns of the past few weeks, some doubt whether the pay squeeze will survive the first nurses' march.

''The Cabinet will keep running from crisis to crisis,'' said Joe Rogaly, political columnist in the Financial Times. ''There will be no respite until, by accident or design, the recession begins to end.''

Major was forced to pull the plunging pound from Europe's currency system on Sept. 16 and devalue it - after promising never to do so. A controversial Cabinet minister he'd defended bowed to media pressure and quit a week later. Then Major retreated rapidly from the plan to lay off 31,000 miners.

Major, 49, once greatly liked, is now accused of indecision and drift.

A Market Opinion and Research International poll published in this week's edition of The European newspaper said only 16 percent of people now have confidence in Major, and 77 percent are dissatisfied with his leadership.

The negative rating was four points lower than that of Mrs. Thatcher in the months before she was ousted in a November 1990 party revolt.

The poll of 1,082 adults had a margin of error of 3 percent.

As for European union, which has split his own party, Major has pledged to submit a ratification bill to the House of Commons by early next year and has staked his political future on getting it passed.

Some Conservatives fear Britain will have to surrender its sovereignty in order to join Europe. But Major sees unity as crucial.

''It may be the ambition of some to see this country isolated as a sour little outpost of western Europe, but it is not my ambition,'' Major told the House of Commons on Tuesday.