WASHINGTON (Reuters) - The Trump administration is denying and delaying more skilled-worker visa petitions than at any time since at least 2015, in keeping with its promise to increase scrutiny of foreign workers, according to data the government released on Friday.

U.S. officials say they have made reforms that prioritize American workers, cut down on fraud and streamline the immigration process. But lawyers who help employers apply for the visas say the agency is rejecting legitimate applications and tying up requests in bureaucratic red tape.

The data provided by U.S. Citizenship and Immigration Services (USCIS), the agency that adjudicates the visas, extends to the 2015 fiscal year, encompassing the last two years of the Obama administration and the first two years of the Trump administration.

Republican President Donald Trump campaigned in 2016 on restricting immigration, and early in his presidency issued an executive order directing the Department of Homeland Security, which oversees USCIS, to tighten its policies on H-1B visas. The visas are intended for foreign workers who generally have bachelor’s degrees or higher to work in the United States, often in the technology, healthcare and education sectors.

In the 2018 fiscal year, which ended on Sept. 30, the government issued “initial denials” to over 61,000 H-1B applications. In that time, the government issued decisions on over 396,000 applications.

That is more than double the number of such denials over the prior year, even as the total number of applications the government completed dropped by about 2 percent between 2017 and 2018.

And denials look set to increase even further this year. In the first quarter of the 2019 fiscal year, the government issued initial denials to nearly 25,000 H-1B applications, a 50 percent increase over the same period last year.

The majority of petitions are still being approved, but the approval rate is dropping. In 2015, the approval rate was 96 percent, compared with 85 percent last year.

“USCIS has made a series of reforms designed to protect U.S. workers, increase our confidence in the eligibility of those who receive benefits, cut down on frivolous petitions, and improve the integrity and efficiency of the immigration petition process,” said Jessica Collins, a USCIS spokeswoman.

The government data also show that the administration is issuing far more “requests for evidence” in response to H-1B applications. Such requests, or RFEs as they are known, often challenge the basis of the original petitions and require employers and attorneys to submit additional paperwork. Receiving an RFE from the government can add several months and thousands of dollars in legal fees to the cost of applying for a visa, attorneys say.

The number of completed H-1B petitions that drew an RFE reached over 150,000 last year, compared with 86,000 in 2017, a 75 percent increase.

Ron Hira, a professor at Howard University and critic of the H-1B program, said the data suggests USCIS is giving employers a fair opportunity to justify their petitions through the RFE process.

“It also makes one question whether the Obama administration was doing an adequate job in ensuring the integrity and accountability of the H-1B program,” Hira wrote in an email.

He also noted that large tech companies, such as Microsoft Corp, Amazon, Alphabet Inc’s Google and Facebook Inc, enjoyed H-1B approval rates last year of 98 percent or 99 percent, according to USCIS, while firms that have been criticized for using H-1B workers to replace Americans saw their petitions approved at far lower rates.

But immigration attorneys say many of the denials and RFEs are violating the laws and regulations governing the program.

Some companies are successfully challenging the denials in federal court. Entegris Professional Solutions, a Minnesota company, sued USCIS in December over the rejection of an H-1B application for one of its employees.

This month, USCIS reopened the case and granted the petition, said Matthew Webster, one of Entegris’ attorneys on the case.