TRENTON — New Jersey Treasurer Andrew P. Sidamon-Eristoff last night told Democratic leaders their budget proposal is "unconstitutional" and warned them that if it remains unchanged the governor will use his "full range of constitutional remedies," according to a letter obtained by The Star-Ledger.

The letter comes less than 24 hours before lawmakers are expected to vote on the Democrats' $30.6 billion budget proposal, roughly $1 billion higher than the plan Gov. Chris Christie offered.

The treasurer said Democrats are using revenue estimates that are more than $300 million higher than those Christie certified last week, thus running afoul of the law. He also said Democrats "fabricated" higher revenue figures to boost this year’s ending surplus.

"This budget is not just irresponsible, but ultimately creates a deficit that violates the state’s constitutional obligation to have a balanced budget," Sidamon-Eristoff wrote.

The letter provides a preview of how Christie plans to deal with the Democratic proposal and how he will defend his refusal of elements of the plan on a constitutional, rather than a policy, basis.

Democrats responded Tuesday night that they are not obligated to use the governor’s revenue estimates, and they are holding out hope that he will adjust them upward when he considers their budget proposal.

Democrats are relying on estimates provided by the nonpartisan Office of Legislative Services, which they say historically has a better track record than whoever is sitting in the governor’s office.

"This ridiculous letter is the clearest sign yet that the Republicans are panicking over the prospect of opposing a responsible budget that protects middle-class property taxpayers and seniors, restores health care for women and creates jobs," Assembly Democratic spokesman Tom Hester said.

"The governor should either practice his talk of bipartisan compromise and sign this budget or own up to his drastic cuts," Hester said.

Democrats want to use the additional revenue to provide $1.1 billion in additional funding for schools, including roughly $500 million for the Abbott districts as required by the state Supreme Court. They also want to provide tax relief to seniors and working-class residents.

The treasurer also criticized Democrats for overestimating cost savings from the health and pension overhaul. Christie initially targeted those savings at $323 million, but he now expects much less due to changes in the final legislation.

Before they included it in their own budget, Democrats had called the governor’s savings estimates inflated.

Sidamon-Eristoff warned Democrats that Christie would be forced to rectify the situation if the budget as proposed is approved, but he did not provide specific actions the governor would take.

"If they are not resolved, the Legislature would have failed in its unique constitutional obligation to enact a balanced budget, in which event the governor would have no choice but to avail himself to the full range of constitutional remedies available to him," Sidamon-Eristoff wrote.

Christie has the power to veto any line item out of the budget, or trim spending. Democrats do not hold a veto-proof majority.

Earlier Tuesday, Republican lawmakers accused Democrats of misleading the public with their budget

"They are trying to get their street cred back," said state Sen. Kevin O’Toole (R-Essex), referring to the recent passage of health and benefit reforms that pitted unions against Democratic leaders. "At the end of the day, their plan is not sustainable and I can’t see this governor signing a budget that takes us down a path that he’s worked so hard to avoid."

Democratic lawmakers are united behind their budget, making it likely that it will be approved Wednesday by both legislative chambers along partisan lines and sent to the governor’s desk.