Donald Trump has directed officials to toughen rules for asylum seekers, including by introducing a fee for their applications and barring those who entered the country illegally from working until their claims are approved.

The moves are the latest effort by the Trump administration to restrict asylum, a process meant to protect people fleeing persecution and violence in their home country. Many of the changes would be dramatic shifts in how asylum seekers are treated, but would also require time-intensive regulatory procedures before they go into effect, which will probably take months.

Trump administration officials have for more than two years blamed US laws protecting asylum seekers for encouraging fraudulent or non-deserving claims, but have provided little evidence that such widespread fraud exists.

On Monday, Trump signed a presidential memorandum that directed the justice department and Department of Homeland Security to, within 90 days, introduce a slew of new regulations tightening asylum policy, including one setting a fee for asylum applications, which are currently free to file.

Even a small fee could be insurmountable for many asylum seekers, said Victoria Neilson, a former official at US Citizenship and Immigration Services, the government agency that accepts asylum applications.

“The majority of people coming to the United States seeking asylum are coming with little more than the shirts on their back,” she said.

Another regulation Trump ordered his officials to prepare would ensure asylum claims are adjudicated in immigration court within six months.

US law already directs the justice department to finish asylum cases within six months, but with a backlog of more than 800,000 cases, asylum claims often take years to come to a conclusion.

“The provision to process cases in 180 days has been on the books for over two decades,” said Ashley Tabaddor, president of the immigration judges’ union. “The problem is that we have never been given adequate resources to adjudicate those claims in a timely fashion.”

Asylum cases are often complex and involve trauma, and judges should have discretion to provide more time depending on the case, Tabaddor said.

Trump also ordered officials to introduce regulations that would disqualify asylum seekers who entered the country illegally from obtaining work permits while their claims are pending. Currently, asylum seekers who enter both legally and illegally are allowed to work while their claims wind through the courts.

US Customs and Border Protection officials encountered some 100,000 people at the US-Mexico border in March, the highest level in more than a decade, and one which officials say is pushing resources to the breaking point.

The Trump administration has so far failed to stem the flow of people approaching the border or to put in place measures that ease the impact on immigration officials and border cities responding to the increase.

This latest memo is a test for the new acting homeland security secretary, Kevin McAleenan, who took up the post earlier this month after several top immigration officials were forced out. The officials, including the former DHS secretary Kirstjen Nielsen, were reportedly forced out for not being aggressive enough in delivering Trump’s restrictionist immigration agenda.

These officials oversaw controversial policies including family separation and the administration’s previous efforts to make it more difficult for people to seek asylum.

Last year, the Trump administration attempted to block people from seeking asylum outside of legal ports of entry, said women who are victims of domestic or gang violence no longer qualify for asylum and ordered people seeking asylum at the border to stay in Mexico while their claims were processed. Federal judges blocked each of these efforts, and the supreme court ruled the so-called “asylum ban” violated the US constitution.

Under US law, asylum seekers that have a credible fear of return can seek review in immigration courts. The large majority of asylum seekers eventually lose their cases but can live in and work in the United States for the months or years it takes to process their claims.

But immigrant advocates say those rates represent the failures of immigration court, not solely the legitimacy of claims. Most asylum seekers do not have legal representation in the courtroom, which greatly improves their chances of winning an asylum claim. The delay between entering the country and appearing in court, which often last years, is also said to harm their cases.

The inefficiency of the courts, which become more chaotic with each rule change and ensuing legal action, also makes it more difficult to root out the illegitimate cases, advocates say.

Archi Pyati, chief of policy at Tahirih Justice Center, a not-for-profit that assists immigrant women and children, said the new regulations would make it almost impossible for asylum seekers to access their rights.

“The current proposal is another example of downright poor policy, and is also heartless,” Pyati said in a statement. “This scheme will fail to bring protection to those who need help, and will cripple the already broken system even further.”

On Tuesday morning, Trump appeared to defend the decision by tweeting about immigration and drug cartels in Mexico, who largely transport their drugs to customers in the US through legal ports of entry.

“They have labs nearby where they make drugs to sell into the U.S. Mexico, one of the most dangerous country’s [sic] in the world, must eradicate this problem now,” he tweeted. “Also, stop the MARCH to U.S.”

Trump continued to say that Democrats must vote to change immigration laws that are “weak, ineffective and dangerous”.

Julián Castro, the former mayor of San Antonio who is seeking the Democratic nomination for president, called Trump’s memo “truly sickening”.

“Families are fleeing violence and turmoil to seek refuge at our borders and Donald Trump wants to charge them a fee to gain asylum,” Castro tweeted.