Donald Trump’s appointment of a close political ally with no intelligence experience to lead the nation’s spy agencies has thrown last-ditch efforts to renew a critical surveillance program into doubt.

Bill Pulte, currently head of the Federal Housing Finance Agency (FHFA), major Republican donor and heir to a home construction fortune, was tapped by Trump to serve as acting director of national intelligence days after Tulsi Gabbard departed the role.

Senior Democrats immediately said the move could doom a fragile bipartisan agreement to renew section 702 of the Foreign Intelligence Surveillance Act, which is due to expire next week.

Section 702 permits US intelligence agencies to collect communications of foreign targets operating outside the country without a warrant. Congress is working toward a deadline of 12 June.

The powerful intelligence tool has long attracted controversy, since the program targets foreign nationals whose messages may pass through US servers or involve US contacts, meaning a wide array of domestic communications can be swept up without a warrant ever being sought.

The FBI in 2020 was discovered using section 702 to investigate whether protesters involved with Black Lives Matter had any ties to terrorists, according to a declassified memo released by the office of the director of national intelligence in 2023, a seat that would soon be filled by Pulte.

Mark Warner, a Democrat and vice-chair of the US Senate intelligence committee, trashed Pulte’s lack of experience for the position. “What qualifications from my standpoint does Mr Pulte bring to the office? Well, he has shown that he is willing to do anything that President Trump wants, legal or otherwise,” he said during a hearing on Tuesday.

In an interview with NPR on Wednesday morning, Warner went further, saying that Pulte’s appointment had upended what he described as an already difficult path to renewal of section 702. “I do not have the confidence I had yesterday,” he said, adding that the move amounted to placing “someone with no intelligence background, any record of misusing private information, in charge of Director of National Intelligence” at the worst possible moment.

The pressure is also being applied privately. Punchbowl News reported that Warner had personally asked John Thune, the Senate majority leader, to use his influence with the White House to reverse the appointment, with Democratic sources making clear that a bipartisan deal on 702 could collapse if Trump refuses.

Thune, for his part, offered a notably cool response to his own president’s pick. He told reporters that “we don’t need a weaponized” national intelligence director and warned Pulte would face “a lengthy road ahead of him” if nominated permanently. Asked about fears that Pulte could use the intelligence community to target Trump’s political opponents – as critics say he did at the FHFA, where he leveled unproven fraud allegations against figures including Lisa Cook, the Federal Reserve governor – Thune said: “We need professionals there.”

Cook has denied wrongdoing. Trump tried to use the allegations to remove her from the Fed’s board. She refused to step down, setting the stage for a legal battle which is now being considered by the US supreme court.

Chris Murphy, a Democratic senator of Connecticut, also expressed concern. “The very nature of our collection is now going to be put in the hands of somebody who has a history of seeking out private information for political gain,” he said.

The bill currently being circulated by Tom Cotton, the Senate intelligence chair, and Chuck Grassley, the judiciary chair, would extend 702 through June 2029, and includes new penalties for intelligence abuses and additional FBI search requirements. It also carries a three-year ban on the Fed issuing a digital currency, a concession to House hardliners, though Democratic support is needed to clear the bill past the 60 vote threshold.