Mayor Antonio Villaraigosa is asking federal officials to rethink their policy on workplace immigration crackdowns that involve established businesses and to focus on employers that mistreat workers instead.

The mayor said in a letter to Homeland Security Secretary Michael Chertoff that work-site raids by Immigration and Customs Enforcement could have “severe and long-lasting effects” on the local economy, the Los Angeles Times reported Thursday.

ICE made more than 4,900 work-site arrests nationwide in fiscal 2007, a 45-fold increase over the number in 2001, authorities said.

More than 130 undocumented workers were arrested at a San Fernando Valley manufacturing company in February and over 60 workers were arrested for immigration violations at South Bay-area warehouses last week.

Los Angeles companies such as clothing manufacturer American Apparel Inc. have reported being questioned by ICE officials about their hiring procedures.

Villaraigosa accused federal officials of targeting “established, responsible employers” in industries that rely on “workforces that include undocumented immigrants.”

“In these industries, including most areas of manufacturing, even the most scrupulous and responsible employers have no choice but to rely on workers whose documentation, while facially valid, may raise questions about their lawful presence,” he wrote in the March 27 letter.

He said ICE should spend its limited resourcestargeting employers who exploit wage and hour laws.

Chertoff has not responded to the mayor’s letter, but Homeland Security spokeswoman Laura Keehner said the department believes its priorities are correct.

She said work-site investigations focus on national security and public safety and that the agency also investigates companies it believes may have committed visa fraud, money laundering, and other violations.

Mayoral spokesman Matt Szabo said Villaraigosa and Los Angeles business leaders hope to discuss their concerns with Chertoff in person next week during an annual business trip to Washington.