Amid charges that Prime Minister Margaret Thatcher was undermined by her own party, an opinion poll released today indicated three candidates for her job would bring the Conservatives an election victory. Under Mrs. Thatcher's leadership, the governing party had trailed Labor in opinion polls for 16 months. Labor is the main opposition party in Parliament. But a poll of about 1,100 voters Friday found that more voters preferred either former Defense Secretary Michael Heseltine or Chancellor of the Exchequer John Major, to Labor Party leader Neil Kinnock. Foreign Secretary Douglas Hurd would put the Tories neck and neck with Labor, with Hurd having a slight edge, according to the poll, taken by ICM for the Sunday Correspondent newspaper. The poll was published today. Forty-seven percent of people asked would vote for Heseltine, compared with 38 percent who would vote Labor, according to the poll of 1,139 people. Major received 46 percent of the vote, compared with 39 percent for Labor, and Hurd had 43 percent of the vote, compared with Labor's 41 percent, the poll showed. No margin of error was given. No poll can be 100 percent accurate, however, and there is usually a margin of error of at least two or three percentage points with a sample of that size, poll watchers said. The 372 Conservative Party members of the House of Commons will vote for a leader on Tuesday. If none of the three candidates receives a majority, a third ballot will be held Thursday. Mrs. Thatcher resigned on Thursday, after it appeared she would lose a Conservative Party leadership vote to Haseltine, who had made a strong showing in a first round of leadership balloting last Tuesday. Hurd and Major, Cabinet ministers no longer shackled by loyalty, immediately jumped into the leadership contest with Heseltine. The latest poll is similar to the findings of a Harris poll released Friday by Independent Television News that also predicted an upturn in Conservative Party fortunes under a new prime minister. That poll, of 1,107 voters on Thursday, found that the Conservatives, with any of the three candidates as leader, would beat Labor if a general election were held immediately. A general election must be held before mid-1992. The poll found voters ranked the candidates in the same order - with Heseltine leading Labor by 10 points, Major by seven points and Hurd by four. No margin of error was given in the Harris poll. Supporters of the 65-year-old Mrs. Thatcher have angrily accused Conservatives of what one called ``political matricide'' in forcing her to quit after 15 years as party leader and 11{ years as prime minister. High inflation, rising interest rates, an unpopular new tax and her lone opposition among European Community leaders to financial and political integration were among factors that undermined her support. Cabinet colleagues and campaign managers told her she could not muster enough support to win in further balloting next week. Her opponents in the party feared that under her continuing leadership the Conservatives would lose to Labor at the next general election. Labor has been in opposition since 1979. Conservative legislators returning home for the weekend were met Friday by anger from grass-roots backers of Mrs. Thatcher. Peter Stainforth, local Conservative Party treasurer at Stevenage, about 25 miles north of central London, reported particular rancor over Sir Geoffrey Howe. The deputy prime minister quit on Nov. 1 and bitterly attacked Mrs. Thatcher in a Commons speech on Nov. 13. ``I cannot express how the constituency feels about that latter-day Brutus who was the first to plunge his dagger into his leader's back,'' Stainforth said.