The Trump administration is facing growing calls to invest more federal enforcement resources to investigate the threats posed by far-right US domestic terrorism in the wake of the mass shooting in El Paso, Texas, on Saturday and in Gilroy, California, a week earlier.

Both shootings are being investigated by federal authorities as domestic terror attacks after authorities said that the gunman in each shooting, each of them young men, had been informed by violent ideology before the respective attacks.

In El Paso, where at least 22 people were killed, the 21-year-old white gunman, who is now in custody, is believed to have posted a hate-filled message laden with anti-immigrant rhetoric on the far-right website 8chan minutes before carrying out the attack.

In Gilroy, where three people were killed, the 19-year-old gunman, of mixed heritage, who was killed by law enforcement, was said by investigators to have written a list of potential targets. The authorities continue to examine his potential motives and have not ruled out white nationalism.

Experts say that both the Obama and Trump administrations have not diverted enough federal resources to pursue terrorism tied to white extremism, pushing most counter-terror efforts to fighting groups associated with extremist Islam in the wake of the September 11 terrorist attacks.

This, despite the fact that since 2002 the number of people killed in attacks linked with extremist Islam is slightly less than those associated with white nationalism. According to research by the New America, 104 people were killed in domestic terror attacks by jihadists while 109 people have been killed in attacks by white nationalists.

But the Trump administration has further dismantled efforts to combat far-right extremism in recent years. The administration cancelled two large federal grants worth over $1m, sanctioned by the Obama administration, one to a program called “Life After Hate”, which rehabilitates former extremists, and another to the University of North Carolina, aimed at countering violent extremism online.

People pray at a makeshift memorial honoring victims of the El Paso shooting, on Tuesday in El Paso, Texas. Photograph: Mario Tama/Getty Images

“This all indicates this is a low priority issue for this administration,” said Heidi Beirich, a researcher at the Southern Poverty Law Center. “The president has said this himself, that it’s a low priority issue even as the bodies have been piling up after these attacks.”

Trump, whose presidency and campaign have been marked with racism directed towards Muslims and Latino immigrants, has been reticent to tie the El Paso attack to white nationalism. Following the white nationalist attack on two mosques in Christchurch, New Zealand, which claimed the lives of 51 people in March this year, Trump refused to describe white nationalism as a growing global threat.

“I think it’s a small group of people that have very, very serious problems,” Trump said at the time. The president also praised “very fine people on both sides” of a far right rally in Charlottesville in August 2017, which drew KKK members, neo-Nazis, and white supremacists and led to the murder of a counter-protester, Heather Heyer, during violent clashes.

Despite this, senior law enforcement officials in America have routinely articulated concerns about the rise of far-right terrorism in the United States and internationally.

The FBI director, Christopher Wray, recently told the US Congress that the bureau had arrested about 100 domestic terror suspects in the past nine months and that “a majority of domestic terror cases we’ve investigated are motived by some version of what you might call white supremacist violence”.

Immediately after the El Paso attack at the weekend, a group of six former National Security Council members for counter-terrorism wrote a bipartisan statement urging the Trump administration to make domestic terrorism “as high a priority as countering international terrorism has become since 9/11”.

The statement continued: “This also means providing a significant infusion of resources to support federal, state and local programs aimed at preventing extremism and targeted violence of any kind, motivated by any ideology or directed at any American community. We simply cannot wait any longer.”

Although FBI resource allocation is opaque, there are numerous insider accounts to suggest the issue is not a priority internally, despite the bureau’s remit to combat domestic terrorism and far-right extremism.

“White supremacy is the lowest priority,” a retired FBI agent with direct knowledge of terrorism investigations told the Daily Beast in October last year. “I would say the threshold to initiate an investigation is much higher for subjects of white supremacy investigations than it is for a Muslim, frankly.”

A woman holds a sign during a rally against guns and white supremacy in the wake of mass shootings in Dayton and El Paso in front of the White House on Tuesday. Photograph: Kevin Lamarque/Reuters

In 2009 an internal Department of Homeland Security memo warned of the growing threat posed by rightwing extremism in the wake of the 2008 presidential election and the financial crisis. After the report was leaked to the media, it prompted a backlash from Republicans against efforts to combat violent white nationalism.

According to the report’s author, the former senior domestic terrorism DHS analyst Daryl Johnson, his unit was mothballed and all work related to far-right extremism was abandoned.

Experts now, as then, describe that decision as a major mistake.

“White nationalism is not going anywhere because it’s indigenous,” said Beirich. “It’s not going to disappear. It’s a part of our societies. So this danger, as the west becomes more diverse isn’t going to dampen down it’s going to accelerate.”

She added: “The first domestic terror group in US was KKK, after the civil war, that’s how far back this dates.”