Major Calls Vote of Confidence on Treaty : Britain: Prime minister loses critical Commons test on ratifying Maastricht pact on European union.

The British government was thrown into turmoil late Thursday when Prime Minister John Major lost a critical House of Commons vote on approval of the Maastricht Treaty on European union.

Major immediately called for a vote of confidence in Parliament today that will firmly decide whether the treaty, after 18 months of debate, will be ratified--or whether the government will fall and new elections be called.

Thursday’s voting climaxed one of the most bitter episodes of infighting in modern British parliamentary history.

Most political experts said the opposition Labor Party could win a general election today, given the low standing in the opinion polls of Major’s Conservative government.

And observers added that, though the government could survive a vote of confidence, the Conservative Party had self-inflicted wounds that might take years to heal.

In Thursday’s complex voting, some members of Parliament crossed party lines and left even parliamentary experts mystified.

The Maastricht Treaty, named after the Dutch city where the treaty calling for closer European political and economic union was signed in 1991, was finally approved this week by both the House of Commons and the House of Lords.

But earlier this year, in one of the acrimonious sessions involving ratification, Major agreed to a later vote on a resolution about what is called the “social chapter” of the treaty.

This is a provision that Major objected to in Maastricht. But the 11 other European Community nations signed the pact, which provides certain protections for the labor force in European Community countries.

The opposition Labor Party and the Liberal Democrats are in favor of including the “social chapter” in the treaty, and they voted for it. They were joined by some renegade anti-unity Conservatives who are against the entire treaty.

The vote on the social chapter was the first one held Thursday evening and resulted in a tie of 317 to 317. House Speaker Betty Boothroyd then cast the deciding vote in favor of the government.

But a second vote to ratify the entire treaty, incorporating the government’s position against the social chapter, was narrowly defeated, 324 to 316, amid jubilant scenes on opposition benches in the Commons.

This had left the position on Maastricht up in the air until Major declared that he would insist on a vote of confidence in his government today.

The vote is to link the future of his government to approval of the resolution on the social chapter. It is designed to force anti-unity Conservatives to support the government--or see its downfall.

Late Thursday, political analysts were predicting that Major will squeak through today’s vote. But they said his prestige will be badly dented because of his inept handling of the Maastricht ratification process and his failure to quell the revolt in his own party’s ranks.