Immigration officials said yesterday that illegal immigrants whose temporary work permits expire while they await word on their amnesty petitions will be given two-month extensions.

Mark Everson, deputy commissioner of the Immigration and Naturalization Service, made the announcement at a special news briefing on the one-year anniversary of the signing of the immigration law. The one-year amnesty program for illegal immigrants is at its halfway point.

When illegal immigrants apply for amnesty they receive a temporary work permit that is good for six months. The permits of the May applicants have expired. Immigrant advocacy groups had feared that some illegal immigrants would lose their jobs if their temporary work permits expired before they received final word on their amnesty petitions.

Everson said the INS decided to grant the extensions because the agency has processed only about 71 percent of the 38,400 amnesty applications it received in May. Amnesty is a four-step process that leads to permanent residence.

Of the May applications that are still pending, Everson said about 22 percent will receive word within a few days and the rest will receive letters informing them they can receive a two-month extension of their work permit at their local legalization center.

Spokesmen for several immigrant rights organizations said yesterday in a separate news conference that the INS had made some favorable changes in the amnesty program but chided the agency for not conducting a more aggressive public information campaign and for taking too long to process the applications.

Muzzafar Chishti, immigration project director for the International Ladies Garment Workers Union, said the delays in processing the applications is having a ripple effect among illegal workers.

"We have too many cases where one member in a shop went and applied in July and the others are waiting for his approval to come in before they apply," he said.

Overall, the INS has approved 120,000 illegal immigrants for legalization and has denied the applications for 2,200, Everson said. Most of those cases were filed in May and June.

As of the end of October, 758,387 persons had applied for amnesty.

INS officials said computer problems and changes in procedures for handling the applications were to blame for the delays.

"It's a logical decision we made in the last few days," Everson said. "We've been working to get the open number down and we said what's the fair thing to do, and we decided to allow the individual alien who feels he needs an extension to come in and get one at no cost."

Everson also said INS officials suspect that about half of the 42,000 applications for legalization filed by farmworkers in Florida under a separate Seasonal Agricultural Worker (SAW) program are fraudulent. Under the SAW program, farmworkers who have worked in the United States for 90 days or more prior to May 1, 1986, are eligible for amnesty.

Everson said the INS has dispatched a special team of investigators to Florida to review the SAW applications, and he expects criminal prosecutions in some cases.