A lack of funding due to the partial shutdown of the US government is hindering FBI investigations into drug and terrorism offences, the FBI Agents Association (FBIAA) has said.

The bureau has lost several informants who have infiltrated groups under investigation, an anonymous FBI agent was quoted as saying in a report on the impact of the shutdown.

“We have lost several sources who have worked for months, and years, to penetrate groups and target subjects. These assets cannot be replaced,” the joint terrorism task force coordinator said.

Agents who had been working on an investigation into the MS-13 criminal gang said they were only able to communicate with Spanish-speaking informants through a conference call with a translator.

“Since the shutdown, I have not had a Spanish speaker in the division,” one agent said. “We have several Spanish-speaking informants. We are only able to communicate using a three-way call with a linguist in another division.”

Trump shuts down US government over Mexico border wall – in pictures Show all 15 1 /15 Trump shuts down US government over Mexico border wall – in pictures Trump shuts down US government over Mexico border wall – in pictures Federal workers and contractors rally against the partial federal government shutdown Getty Images Trump shuts down US government over Mexico border wall – in pictures The US Capitol on the first morning of a partial government shutdown in Washington EPA Trump shuts down US government over Mexico border wall – in pictures Federal workers and contractors rally against the partial federal government shutdown Getty Trump shuts down US government over Mexico border wall – in pictures President Trump speaks with children who called the North American Aerospace Defense Command Santa tracker in the State Dining Room of the White House. He earlier in the day, tweeted that he was 'all alone in the White House' waiting for Democrats to make a deal on border security EPA Trump shuts down US government over Mexico border wall – in pictures Furloughed federal workers pick up free food at a pop-up store of Kraft Heinz Getty Images Trump shuts down US government over Mexico border wall – in pictures Hundreds of federal workers and contractors rally against the partial federal government shutdown Getty Trump shuts down US government over Mexico border wall – in pictures A pedestrian walk past the U.S. Capitol ahead of a possible partial government shut down in Washington, U.S., December 20, 2018. REUTERS/Joshua Roberts JOSHUA ROBERTS Reuters Trump shuts down US government over Mexico border wall – in pictures From left, House Majority Leader Steny Hoyer, Senate Minority Leader Chuck Schumer, Sen. Dick Durbin and Speaker of the House Nancy Pelosi walk to speak to reporters after meeting with President Donald Trump about border security in the Situation Room of the White House. Trump declared he could keep parts of the government shut down for "months or even years" as he and Democratic leaders failed in a second closed-door meeting to resolve his demand for billions of dollars for a border wall with Mexico Evan Vucci AP Trump shuts down US government over Mexico border wall – in pictures Federal workers and contractors rally against the partial federal government shutdown Getty Images Trump shuts down US government over Mexico border wall – in pictures A sign alerts visitors to the closure of the National Archives on the fifth day of a partial government shutdown EPA Trump shuts down US government over Mexico border wall – in pictures Hundreds of federal workers and contractors rally against the partial federal government shutdown Getty Images Trump shuts down US government over Mexico border wall – in pictures Visitors read signs announcing the closure of the White House Visitor Center EPA Trump shuts down US government over Mexico border wall – in pictures President Donald Trump speaks during a round-table discussion on border security and safe communities with State, local, and community leaders in the Cabinet Room of the White House Getty Images Trump shuts down US government over Mexico border wall – in pictures A sign alerts visitors to the closure of the White House Visitor Center on the first day of a partial government shutdown EPA Trump shuts down US government over Mexico border wall – in pictures Furloughed federal workers show their IDs for entering a pop-up store of Kraft Heinz Getty Images

One official said the government shutdown had “eliminated any ability to operate”. They added: “It’s bad enough to work without pay, but we can only conduct administrative functions while doing it. The fear is our enemies know they can run freely.”

The FBI told The Independent it had no comment.

In a statement, the bureau distanced itself from the report, adding: “This report is a product of the FBIAA, a nonprofit professional association, and was not issued by the FBI.”

Several FBI officers said the government shutdown meant they risked losing vital informants.

“Not being able to pay Confidential Human Sources risks losing them and the information they provide FOREVER. It is not a switch that we can turn on and off,” one official said in the report.

FBI Agents Association’s Thomas O’Connor holds up an FBI report ‘Voices From the Field’ giving examples of how the government shutdown is undermining its work (Getty) (Jim WATSON/AFP/Getty Images)

Another agent said they fear losing further informants because they “cannot secure safe spaces to meet with our informants and we cannot pay them for their information”.

Hundreds of thousands of federal workers have gone without pay because of the government shutdown, which shows no signs of a swift conclusion.

Donald Trump has refused to sign any bill that would reopen the government unless it includes more than $5bn (£3.84bn) in funding for a wall across parts of the US-Mexico border.

Donald Trump announces plan to 'end government shutdown' involving border wall funding

Democrats consider a wall ineffective in combatting illegal immigration, and want the president to reopen federal agencies before they enter negotiations over border security.