TRENTON -- With the state Legislature poised to approve a 23-cent-a-gallon increase in the gas tax Wednesday -- along with a decrease in the sales tax and the elimination of the estate tax -- budget analysts and consumer advocates complained bitterly on Tuesday that the average New Jerseyan would pay a lot more at the pump while getting little in the way of tax breaks.

Various efforts by the governor and legislative leaders to replenish the Transportation Trust Fund have repeatedly brought these groups together to warn that the tax cuts will benefit a relatively few wealthy residents while undermining such Democratic priorities as environmental oversight, funds for education and aid for the state's poorer residents.

The latest tax plan, the result of negotiations between Gov. Chris Christie, a Republican, and Democratic leaders in the Senate and Assembly, eliminates the estate tax, raises the Earned Income Tax Credit for the working poor, eliminates taxes on much pension and retirement income, slightly reduces the sales tax and creates a tax break for veterans.

The 23-cent-per-gallon increase on gasoline sold in the state will finance an eight-year, $16 billion transportation program that will draw another $16 billion in federal matching dollars.

The proposal is scheduled for votes in both houses Wednesday and is widely expected to pass.

Opponents of the agreement, which came after months of wrangling and delayed highway construction projects, have argued that while the investment in infrastructure is necessary, the state can not afford the associated tax cuts.

New Jersey's $34.5 billion budget underfunds education, public worker pensions, municipal aid and other programs by billions of dollars.

The plan that lawmakers will vote on Wednesday borrows from proposals offered by Christie as well as Senate President Stephen Sweeney and Assembly Speaker Vincent Prieto, both Democrats.

Christie yielded on the sales tax, accepting a fraction of the one percentage point cut he'd proposed, while Sweeney (D-Gloucester) agreed to tax cuts about $500 million deeper than what he'd earlier deemed fiscally responsible.

"Middle class job growth, better mass transit and tax credits for those who need them most are core Democratic principles we shouldn't shy away from," said Sweeney spokesman Luke Margolis.

A spokesman for Christie did not respond to a request for comment. But Christie has said the deal, which was necessary to raise money for the depleted trust fund, will improve the state's infrastructure and make the state more affordable.

Advocates pushed back Tuesday, saying the compromise includes a huge tax break for the 4 percent of estates that pay the estate tax each year and "invisible savings" to everyone else through the reduction in the sales tax from 7 percent to 6.625 percent.

For the sales tax cut to offset the $170 more a year in increased gas taxes facing the average driver, a consumer would have to spent about $45,000 a year on taxable goods, estimated Analilia Mejia, executive director of the New Jersey Working Families Alliance.

"This is Trenton insanity at the worst that I've ever, ever seen it," Sen. Raymond Lesniak (D-Union) said at the Statehouse news conference.

The estate tax change will see the $675,000 tax threshold on the transfer of estates increase to $2 million on Jan. 1. It would be eliminated altogether after Jan. 1, 2018.

New Jersey levied estate taxes on 3,467 estates in 2014, according to data from the state's nonpartisan Office of Legislative Services. The richest 94 estates paid an average of $1.2 million, while those valued from $675,000 to $1 million paid an average of $21,000.

"The estate tax is a big chunk of the reduced revenues in this deal," said Gordon MacInnes, president of New Jersey Policy Perspective, a left-leaning Trenton think tank. "So what you're talking about is eliminating a very, very special source of revenue for the rest of us by rewarding 95 to 100 families every year with a sweetheart deal that we cannot afford."

Proponents argue eliminating the estate tax, one of two death taxes here, will retain residents and wealth fleeing the state and will ultimately boost tax collections.

Chamber of Commerce President Tom Bracken said previously that the agreement will be "transformational for New Jersey's future and we should all embrace it."

"Eliminating the estate tax, reducing the state sales tax and the other reforms which are part of this package will result in new long term investments in our state, make our tax structure more equitable and our state more affordable," he said.

To be sure, the tax package also has conservative detractors who have announced they will oppose the plan, including Sens. Kip Bateman (R-Somerset), Jennifer Beck (R-Monmouth), Mike Doherty (R-Warren) and Assemblyman Jay Webber (R-Morris).

Their opposition is largely rooted in the gas tax increase, which Webber said Tuesday will "impose a massive, front-loaded, immediate, and permanent 160 percent gas tax increase on New Jersey's overtaxed residents in exchange for still-fictional tax reductions that already stand on shaky ground."

Samantha Marcus may be reached at smarcus@njadvancemedia.com. Follow her on Twitter @samanthamarcus. Find NJ.com Politics on Facebook.