ANCHORAGE, Alaska (AP) _ Federal prosecutors say Exxon Corp. knew for years about charges Exxon Valdez skipper Joseph Hazelwood regularly was host of drinking parties and tossed his empty whiskey bottles overboard.

According to the government, Exxon Corp. knew since 1985 that Hazelwood was diagnosed with two medical problems - episodic alcohol abuse and a type of mood disturbance or depression called dysthymia.

The government also accused Exxon of failing to monitor Hazelwood after he was treated for alcohol abuse in 1985. Monitoring would have revealed that he continued to drink while on duty up to the day of the Valdez wreck, the prosecutors said.

''The Exxon Medical Department had a duty to ensure that Hazelwood was fit to command oil tankers,'' prosecutors said. They called his alcohol abuse and dysthymia problems ''serious'' and ''known to impair judgment.''

These allegations and others about Hazelwood's alleged on-board drinking were contained in the government's response Thursday to Exxon's request that all criminal counts against it be dropped.

Exxon was indicted in February on five counts related to the March 1989 spill. If convicted, the company could be fined more than $600 million.

The Exxon Valdez struck a charted reef and dumped nearly 11 million gallons of North Slope crude oil into Alaska waters. Tens of thousands of birds and mammals died in the nation's worst oil spill.

Court papers said that 19 months before the grounding, Exxon lawyers heard allegations that Hazelwood had regularly held drinking parties aboard ships, tossing empty bottles overboard.

''It was a bad joke in the fleet (that) it's Capt. Hazelwood and his chief mate, Jack Daniels, that run the ship,'' court papers filed by Department of Justice lawyers said.

They said Exxon Shipping company's president only reluctantly agreed to give Hazelwood back his job as tanker master after his treatment for alcohol.

Prosecutors said had Exxon monitored Hazelwood, it would have learned he lost his driver's license only months before the tanker disaster because of a drunken driving conviction.

The prosecutors said Exxon's legal staff knew about the captain's problems for an even longer time - at least since 1982 when it handled a complaint that Hazelwood had ''routinely been intoxicated'' while commanding the huge tankers.

The indictment against Exxon Corp. charges it and its subsidiary, Exxon Shipping, with violating the Migratory Bird Treaty Act, the Refuse Act, the Dangerous Cargo Act and the Clean Water Act.

Charges under the Ports and Waterways Safety Act also accuse the company of negligence by failing to make sure its crew was fit.

Exxon Corp. has tried to distance itself from those charges, saying its tankers are the sole responsibility of the shipping subsidiary.

By detailing its allegations against Hazelwood, and Exxon's failure to know about or stop alleged misconduct, the government has attempted to bolster its case that negligence at the top was a cause of the grounding.

Prosecutors say Hazelwood's alleged impairment caused him to quit the bridge the night of the Valdez grounding, leaving a tricky steering manuever to an unqualified third mate and a helmsman.

The government said Hazelwood knew that the helmsman was incompetent. ''Hazelwood's absence from the bridge was a direct cause of the grounding,'' prosecutors said.

In March, Hazelwood was acquitted of being drunk and reckless and was convicted of one misdemeanor charge of negligent discharge of oil. The conviction is under appeal, along with his sentence of $50,000 in restitution and 1,000 hours cleaning beaches at Prince William Sound.

The Coast Guard dismissed its case against Hazelwood in August.