Fresh from victory in California, consumer activist Ralph Nader brought his campaign to overhaul the insurance industry to the nation's insurance capital last week, calling the industry "fat, lazy, wasteful, and inefficient."

Appearing with Nader at a news conference was Harvey Rosenfield, the 36-year-old author of California Proposition 103.The ground-breaking initiative passed earlier this month rolls back auto and property casualty premium rates, repeals the industry's exemption from state antitrust laws and imposes numerous other changes opposed by the insurance industry.

"We're here to make sure the Connecticut insurance companies hear the message of the California voters," Nader told reporters.

In anticipation of Nader's remarks, Connecticut's insurance companies responded in a united voice, calling Nader's suggested solution to high insurance rates a "prescription for chaos and disaster."

"Cutting insurance rates without cutting the costs responsible for these rates is a transparent attempt to prescribe snake oil remedies for hard realities," said John H. Blair, president of the Insurance Association of Connecticut.

Nader said insurance companies have "underestimated the level of outrage" felt by ratepayers over rapidly increasing premiums. In Connecticut, he said, auto insurance premiums on passenger cars rose 46.6 percent from 1984 to 1988.

He blamed the increase on a lack of competition, state laws that exempt insurance companies from anti-trust laws, and inefficiencies such as bloated middle management staffs and high executive salaries.

Nader saved his strongest criticism for Hartford-based Aetna Life & Casualty Co., which he said is "more aggressive and more cruel than any other insurance company."

He pointed to the company's ad campaign against "lawsuit abuse" in which the company uses the slogan, "Enough is enough."

He described the ads, appearing now in newspapers in Denver, New Orleans, St. Louis and Rochester, N.Y., as "collective jury tampering" in an effort to reduce the amount jurors would award in lawsuits.

Plaintiffs' lawyers and district attorneys in Colorado have made similar charges recently, claiming the ads are misleading and possibly in violation of state laws against deceptive trade practices.

Jason Wright, a spokesman for Aetna, said the company will not be intimidated into dropping the ads.