Four influential Senate Republicans have sent a letter to colleagues voicing strong opposition to comprehensive immigration legislation headed to the Senate floor, warning it will not secure the nation’s borders.

Sens. Ted Cruz (Texas), Chuck Grassley (Iowa), Jeff Sessions (Ala.) and Mike Lee (Utah) said in a June 4 letter the immigration bill repeats the mistakes of the 1986 immigration reform law.

“In 1986, the American people were promised that, in exchange for granting legal status to illegal immigrants, the border would be secured and the law enforced. Washington broke these promises,” they wrote. “Unfortunately, the so-called ‘Gang of Eight’ immigration bill, S. 744, repeats these mistakes.”

Cruz is a fast-rising Tea Party star, Grassley is the ranking Republican on the Judiciary Committee, Sessions is the ranking Republican on the Budget Committee and Lee is another Tea Party favorite.

The group, all members of the Senate Judiciary Committee, said the panel’s markup of the legislation last month made it worse.

Notably, Sen. John Cornyn (R-Texas), who voted against the bill in Judiciary, did not sign the letter. Some Democrats think he may ultimately support the legislation.

Four members of the Gang of Eight on Judiciary, including Sens. Lindsey Graham (R-S.C.) and Jeff Flake (R-Ariz.), often voted in unison to defeat changes Republicans proposed to strengthen enforcement provisions.

For example, the panel rejected an amendment sponsored by Lee to require illegal immigrants to pay back taxes before receiving legal status; a Grassley amendment to require the implementation of the new employment verification system within 18 months; and another Grassley proposal to require effective control over the southern border for six months before granting legal status to 11 million illegal immigrants.

“The bill’s already serious flaws were exacerbated by the adoption of several amendments that significantly weaken current law, hamstring law enforcement, and further complicate our legal immigration system,” Cruz, Grassley, Sessions and Lee wrote.

They highlighted several amendments approved in committee that they believe would weaken enforcement of immigration law.

They cited an amendment sponsored by Sen. Chris Coons (D-Del.) that would prohibit border patrol agents from returning illegal entrants to Mexico during nighttime hours; an amendment sponsored by Sen. Richard Blumenthal (D-Conn.) to limit enforcement actions at college campuses and hospitals; and another Coons proposal to give judges more discretion to halt deportations.

Grassley said in an interview Tuesday that he could vote for the bill on the floor, but only if changes were made to strengthen the border provisions and protect American workers.

“We want immigration reform to pass, but only if it actually fixes the broken system, rather than allowing the problems to grow and fester,” he and his colleagues wrote.

–This report was updated at 7:37 p.m.