Immigration enforcement agents have been banned from labor offices amid fears undocumented migrants are being put off pursuing wages owed to them.

And state workers have been ordered not to reveal workers' whereabouts as lawyers and campaigners have warned migrants could have reason to fear attending labor dispute hearings under Donald Trump's presidency.

Multiple reported cases of Immigration and Customs Enforcement (ICE) agents appearing at immigrants’ hearings prompted California Labor Commissioner Julie Su to release a memo to employees instructing them to refuse immigration agents entry to labor commission offices or to provide information on the location of workers.

A spokeswoman for ICE, Virginia Kice, said in an email that the agency had guidelines to prevent employees from becoming “involved in labor disputes.” She disputed the assertion that ICE agents had appeared at labor commission offices seeking particular people, writing that “ICE has canvassed its enforcement personnel in the greater Los Angeles area and has obtained no information to corroborate those claims.”

But the reports were credible enough to prod Ms Su into action, and now advocates worry the fallout could mean more exploitation of vulnerable workers.

California law already prohibits employers from using employees’ immigration status to retaliate in labor disputes. In keeping with California politicians' backlash against the Trump administration’s hardline immigration stance, labor officials have vowed to maintain those safeguards.

“Just because the federal administration has changed, our laws and policies have not,” California Labor and Workforce Development Agency Secretary David Lanier said earlier this year. “We will not tolerate the use of immigration status as a tool of retaliation against workers who are pursuing their rights under California law.

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But the California Labor Commission has seen a spike in immigration-related cases of employers retaliating against workers, from 14 last year to 58 already in 2017. And with the appearance of ICE agents at hearings spurring official action, attorneys who work on labor conflicts warned that undocumented immigrants will be more likely to forfeit money they’re owed than seek redress if they perceive bringing a labor case could get them deported.

“There’s huge concern among the advocates about the specter of ICE showing up at the labor commission,” Christopher Ho, a staff attorney for the organization Legal Aid at Work, told The Independent. “If it’s not calculated to have a chilling effect on people bringing wage claims it’s certainly having that effect.”

In the 2015-16 fiscal year, the California Labor Commission reported leveling $43m worth of penalties for labor violations, with the restaurant and construction industries incurring the most citations. A report detailing those numbers pegged wage theft in particular at “staggering levels”.

Advocates say the issue is especially rampant in low-wage industries that rely on immigrant labor, where it can be exceedingly difficult to convince people the merits of pursuing lost pay outweigh the risks. But as it stands, many immigrants already avoid going to authorities for fear of deportation.

“A lot of people do decide to go forward” with cases “because a lot of them are just sick of being exploited, but a lot of people quite reasonably say I've got a family here, I'm risking my deportation,” Mr Ho said.

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Those fears have intensified since a nativist platform propelled Mr Trump to the presidency, Carl Soto, workers' rights coordinator at the National Day Laborer Organizing Network, told The Independent.

“I have seen more folks who would have pursued claims not move forward with it because they’re afraid to file official documents with the state,“ Soto said. ”They’re afraid it makes them more vulnerable to immigration action.“

And while Mr Soto praised Ms Su for taking swift action to reassure immigrant workers, he said the reassurance might not be enough.