The bill’s authors will haggle over how stiff punishments should be for illegal immigrants.

The ambitious proposal to revamp the U.S. immigration system negotiated by the White House and key senators will confront a critical question next week: How tough does it have to be on illegal immigrants to pass?

As the Senate considers the bill, the lawmakers who wrote it will need to persuade skeptical conservatives that the plan does enough to punish immigrants who illegally entered the country.

The bill would offer a path to citizenship for most of the nation’s estimated 12 million illegal immigrants.

House Speaker Nancy Pelosi, knowing Democratic backing won’t be enough to pass the bill, has said it would need support from at least 70 Republicans. In the Senate, passage would require at least half of the Republicans, as well as some conservative Democrats.

Conservative critics have denounced the bill, labeling it “amnesty” -- a politically lethal charge.

When debate begins Monday, lawmakers will haggle over the penalties illegal immigrants should face to become legal residents, then citizens. Should they be forced to leave the country first? How much should they pay in fines? Should they be required to forfeit the Social Security benefits they earned while working illegally?

Sen. John Cornyn (R-Texas), who was heavily involved in the negotiations, said he worried the bill might end up being a repeat of the 1986 Immigration Reform and Control Act.

That law legalized some 2.7 million illegal immigrants, but because mandated enforcement measures were never put in place, millions more are believed to have illegally crossed the border in the hope of citizenship.

“We have to make a basic determination: Will this bill restore respect for our laws?” Cornyn said. “Or will it have the opposite effect and encourage still more disregard for our immigration and border security laws?”

Senators who helped negotiate the bill are aware of those concerns. “What more hurdles can be placed to be sure we do the maximum to avoid the charge of amnesty?” asked Sen. Arlen Specter (R-Pa.). “We are still open to suggestions.”

In crafting the compromise, Specter, his bipartisan group of colleagues and two Cabinet officials had sought to address such an “amnesty” charge. Although the bill would grant probationary legal status to illegal immigrants who were in the country before Jan. 1, 2007, it requires a number of steps to become legal.

Eligible illegal immigrants would be granted “Z visas” as a step toward citizenship. But to get there, they would have to pay a total of $5,000 in fines and $2,000 in processing fees.

Heads of household would have to return to their home country and reenter legally, and all family members would have to pass background checks.

After four years, illegal immigrants who want to renew their Z visas for four more years would have to pass the English proficiency test given to those applying for citizenship.

The bill also includes a provision, championed by Sen. John Ensign (R-Nev.), to effectively bar future citizens from receiving Social Security benefits that they had earned while working illegally, even though they were paying taxes. Ensign’s attempt to add this measure to a bill last year failed by a vote of 50 to 49.

Critics say that would punish illegal immigrants after they have become citizens, possibly leaving them in poverty.

The White House made a similar proposal during negotiations on the current bill.

Sen. Jon Kyl, a conservative Republican from Arizona and one of the principal negotiators, said, “I don’t consider it amnesty.” He insisted that “there is no automatic path to citizenship,” noting that illegal immigrants who fail to apply for probationary legal status or those who commit crimes will be deported.

But Sen. Jeff Sessions (R-Ala.), who will lead debate against the Senate bill, said he would “actively oppose immigration legislation that does not meet the expectations of the American people on important issues such as ... citizenship.”

Immigrant advocates are uneasy about the trend of escalating punishment in the last two years of the debate.

During debate on last year’s Senate bill, fines climbed from $1,000 to more than $3,000 in fees and fines.

A White House proposal floated this year proposed a $10,000 fine on top of $3,500 in fees levied every three years. And at one point in this year’s talks, White House negotiators reportedly suggested fees and fines amounting to $64,000 for a family of four.

“Some politicians appear to have succumbed to sharp increases in penalties so as to as strongly and vigorously as possible deny there’s any whiff of amnesty,” said Jonathan Blazer, an attorney with the National Immigration Law Center.

Blazer warned that fines had reached the point where “many people will simply not be able to afford to come above ground.”

The Senate, however, is very likely to take up proposals next week to increase fees and penalties in a bid to counter the “amnesty” label.

Sen. Kay Bailey Hutchison (R-Texas) has worked with Rep. Mike Pence (R-Ind.) for more than a year on an immigration plan that would not allow immigrants to access any Social Security benefits earned illegally.

The Hutchison-Pence proposal also goes further than the Z visa provision by requiring all illegal immigrants to return home, not just the heads of household.

Some lawmakers argue that there is no way to justify giving citizenship to people who have broken the law, no matter how many hurdles are put in place.

Rep. Brian P. Bilbray (R-Solana Beach) said offering legal status would just draw millions more illegal immigrants to the southern border.

“There is no way we’re going to control illegal immigration if we announce we’re going to reward people who have already broken our laws,” he said.

nicole.gaouette@latimes.com