A widening wine scandal that has left at least 20 persons dead so far from methyl alcohol poisoning today forced Italy to suspend all wine exports until they can be certified safe.

The export freeze, announced at a special European Common Market meeting in Brussels, seemed to confirm the opinion of Italian experts that Italy may face the most serious wine scandal in history.

"There is little doubt this is the worst wine crisis ever," said Burt Anderson, an American who is author of "Vino," the bible of Italian wine, and a wine merchant in Tuscany. "There have been wine crises before, adulterations of the product, but never with this many dead."

The crisis, Anderson said, threatens to "destroy 20 years of Italian effort" to upgrade the quality of its large wine production and build world confidence in the product.

The deaths followed adulteration of some cheap Italian wines with methyl, or wood, alcohol to raise the wines' alcohol content to the average 12 percent. Use of a chemical found in antifreeze to sweeten some Austrian wines last year plunged that country's wine exports into a slump from which they have yet to recover.

Contamination so far has not been found in quality Italian wines normally exported to the United States under labels marked "DOC," or "Denominazione di Origine Controllata." The term refers to Italian laws controlling quality wines from growth through production and sales.

Instead, the scandal has struck cheap bulk wines sold to neighboring European countries for mixing with their own local wines. Also implicated are inexpensive, unpedigreed wines sold here as vino di tavola for regional export and local consumption at bargain rates so low that only adulterated wines can be profitable.

The fact that it is only Italy's cheapest, least controlled wines that have been found to have been adulterated by some wine merchants, however, has brought little consolation to Italian wine producers or the Italian government.

Italy is the world's biggest producer and exporter of wines and the cheap bulk wines and unpedigreed (and underinspected) supermarket wines make up more than 60 percent of Italy's annual production. Quality DOC wines, which have increasingly won respect abroad, make up only about 10.6 percent of the country's output.

Despite enormous differences between quality Italian wines such as the DOC-labeled Barolos, Barbarescos and Chianti Classicos and the cheap product involved in the current scandal, there is concern here that such distinctions are not recognized by many wine buyers.

As word of deaths spread in the past month, country after country in Europe has taken action to ban -- or discourage the drinking of -- all Italian wines.

Denmark today banned all Italian wine imports, a step that both West Germany and Belgium already had taken. Switzerland has seized more than 1 million gallons of suspect wine and France, Italy's largest wine buyer, has seized a total of 4.4 million gallons and announced that it would destroy at least 1.3 million gallons found to have been adulterated.

Britain and Austria, among others, also have warned their citizens to be cautious of what Italian wines they drink.

"The fear tends to be generalized and indiscriminately hit all our wines, even though only some have been involved," said Liugi Veronelli, another noted wine critic. "This offense is going to have serious consequences on our foreign markets."

To the increasing discomfiture of the government, which knows all too well the importance of the $1 billion a year contributed to the economy by its wine sales, the scandal is still growing.

A week ago -- about three weeks after the first Italian died of methyl alcohol poisoning -- Minister of Agriculture Filippo Maria Pandolifi listed 31 wine dealers whose products were suspected. This week the list had been expanded to 65 producers. The assumption is that that number will also be revised upward as a result of the government's crash chemical analysis of wines on the market.

By law, Italian wines, unlike many others in Europe that allow adulteration with sugar, are supposed to be produced only with grapes. Additives are illegal.

"The only reason to adulterate wine is to save time in producing it, and costs," said Anderson, the wine expert. Using sugar to raise the alcohol content of cheap wine costs money, and takes time to work; methyl alcohol is both cheaper and faster -- if illegal and, as the current crisis has proved, potentially deadly.

Methyl alcohol, wine specialists note, is a byproduct of the fermentation process and normally is present in wines, though in minimal, nondangerous doses. Italian wine laws limit the methyl alcohol permissible in wines to a fraction of a percent.

That percentage, according to Italian government officials, has been found to have been exceeded by anywhere from 100 to 200 percent in the wines that have caused deaths, comas and blindness in the past three weeks or so.

Opposition critics, along with some wine experts, have charged that the current scandal followed the government's 1984 decision to suspend previous controls and taxes on the production of industrial methyl alcohol, known as methanol, a substance normally used as paint thinner.

That action, the critics said, allowed a number of wine merchants, mostly in northern Italy, to buy methanol secretly to adulterate their wines.

"The revelation last year that some Austrian wines had been adulterated by [a chemical used in antifreeze] killed Austrian exports," said one Italian wine merchant who asked not to be identified. "And no one died from drinking Austrian wine. Here there are more than a dozen people dead; this is a disaster for Italian wine -- even if only a few wines have been involved."