Despite the threat of a White House veto, the Senate voted 86 to 13 yesterday to expand the Superfund toxic-waste cleanup program nearly fivefold and levy a new tax on manufactured goods to pay for it.

Sen. Robert T. Stafford (R-Vt.), the bill's floor manager, said the margin of approval suggests that a veto could be overridden.

"When the president thinks about the needs of the country, the size of the Senate support and maybe his own niche in history, I think he'll sign the bill," Stafford said.

The vote moves the action on Superfund to the House, where a divisive battle among Democrats has prevented any Superfund measure from reaching the floor.

The Senate bill, formally called the Superfund Improvement Act of 1985, would reauthorize the 5-year-old law through 1990 and provide $7.5 billion to clean up the worst of the nation's toxic dumps.

Its passage, however, was quickly criticized by environmental lobbyists, who contend it is inadequately funded and includes major retreats from the current law's strict standards of liability for toxic pollution.

"The Senate has voted to weaken the cleanup liability provisions to the point where it will be extremely difficult for citizens to hold polluters accountable for the damages they have caused," said Daniel Becker of Environmental Action.

The Reagan administration advocates a smaller Superfund, contending the Environmental Protection Agency cannot effectively spend more than $1 billion a year. According to administration officials, however, President Reagan's veto threat is aimed not at the program's size but at the method the Senate chose to raise the money.

More than $5 billion would come from a .08 percent tax, in essence a value-added tax, on more than 30,000 manufacturers with more than $5 million in annual sales. Industry groups have attacked the VAT as a dangerous precedent and an unfair burden on nonpolluting industries.

"It's a foot in the door," said a spokesman for the National Association of Manufacturers, which fears the tax will become an irresistible tool for attacking the federal deficit.

Many lawmakers also oppose the tax on grounds that it is nothing more than a national sales tax that will fall disproportionately on lower-income groups.

The tax was approved by the Senate Finance Committee, whose chairman, Bob Packwood (R-Ore.), defended it as the fairest revenue measure the panel could find to accommodate the growing needs of Superfund without adding to the federal deficit.

"Every industry that would be subject to this excise tax, as best I can tell, does not want to be subject to this excise tax," he said.

There was no serious attempt on the floor to replace the tax with any other revenue-raising measure. Instead, several senators accused the administration of failing to come up with its own revenue plan for Superfund.

"They've copped out on alternatives," said Sen. David F. Durenberger (R-Minn.). "We're in a quandary here. We're all put in the box of choosing between the politics of toxic waste and the politics of the deficit."

The Senate bill makes few major changes in the Superfund program, which was established in 1980 after New York's Love Canal, Kentucky's "Valley of the Drums" and other highly publicized chemical burial grounds focused national attention on the growing problem of leaking toxic dumps.

In one amendment strongly opposed by environmental groups, lawmakers accepted a provision designed to speed cleanups by allowing the EPA to allocate costs among polluters. Environmentalists regard the change as a serious weakening of the current law's strict liability standard, which holds that any single contributor to a toxic dump may be held liable for the cost of the entire cleanup. EPA officials consider the strict standard a useful enforcement tool, but industry groups argued for less-stringent liability provisions.

Earlier this week, lawmakers narrowly rejected one of the bill's most controversial provisions, an experimental project to compensate victims of exposure to toxic contamination for their medical expenses. The administration and industry groups strongly opposed the provision, fearing it would lead to an open-ended entitlement program.

Backers pledged to keep fighting for some form of victims' assistance. "Thirty-five million people in our society lack any form of health insurance whatsoever, and many of these millions live in areas exposed to the deadly dangers of toxic waste," said Sen. Edward M. Kennedy (D-Mass.).

The Senate also strengthened provisions giving citizens more access to information on hazardous waste in their communities.

In the House, a $10 billion version of Superfund was reported by a bitterly divided Energy and Commerce Committee last July. That measure, regarded as inadequate by environmental groups and several key Democrats, still faces action by three other committees and floor action on it is not expected until mid-October.