SACRAMENTO – Gov. Gray Davis' top budget aide suggested yesterday that the annual vehicle license fee will soon automatically triple, costing the average motorist $158 and yielding $4 billion for the state.

The tax increase, part of Davis' plan to close a record state budget gap, is opposed by Republicans who said a new Legislative Counsel opinion supports their view an automatic tax increase would be illegal.

Tax increases usually need a two-thirds vote of approval from the Legislature, which requires at least two votes from Republicans in the 40-member Senate and six Republican votes in the 80-member Assembly.

The Davis administration contends legislation in 1998 that began phasing in a big cut in the vehicle license fee contains a provision that automatically repeals the reduction when the state lacks money.

"It's not the right thing to do," said Assemblyman John Campbell of Irvine, the lead Assembly Republican budget writer. "It's not the responsible thing to do, and we believe it is not the legal thing to do."

Davis' finance director, Steve Peace, a former state senator from El Cajon, said the administration's position is supported by legal opinions from a number of sources.

Davis said earlier this year he expected the tax increase to be automatically triggered before the new fiscal year begins July 1. Peace was asked to comment on a report that the trigger would be pulled today.

"The thing about triggers is they go 'boom,' and they happen just like that," Peace said. "We will know . . . at the moment it happens, not 20 seconds before and not 20 seconds after."

The state obtained an $11 billion one-year loan this month, but state Controller Steve Westly has warned that the state will run out of cash by September and be unable to borrow more if a new budget isn't enacted.

Peace said the state is in the unprecedented position of having exhausted its internal borrowing resources, as well as the bank-backed guarantees needed to obtain loans from outside sources.

"We have never been in a place before where we are literally running 100 percent on other people's money," he said.

Peace said a "broad scope of attorneys" believes a legal challenge would not temporarily block an automatic tax increase, leaving it in place for at least a year while the battle is fought in court.

"There is consensus that there would be no compelling reason for the court to issue a temporary restraining order," he said, "because there would be no damage that couldn't be rectified by the ultimate decision of the court."

Campbell said imposing a tax increase under a legal cloud is "irresponsible" and could lead to chaos later if the courts determine the money must be refunded to motorists.

In a budget crisis a decade ago, the state took money from schools and pension funds, triggering lawsuits that won repayment later. Meanwhile, the state was able to use the money to help close a huge budget gap.

Campbell said the Legislative Counsel believes Westly is responsible for the trigger, that the tax cannot be triggered unless the state runs out of cash, and if the tax goes up then decisions must be made monthly about whether the increase is still needed.

Peace said the counsel failed to understand that electronic cash reports are made daily, not once a month. He said to prevent unequal taxation of motorists, any increase would have to remain in effect for at least a year.