Rep. Devin Nunes (R-CA) on Saturday accused the FBI of launching an investigation into whether President Donald Trump was an asset of the Russian government to “avenge” the firing of former FBI Director James Comey.

According to the New York Times, law enforcement officials became so concerned by President Trump’s behavior in the days after he terminated Comey that they began investigating whether he had been working for Russia against U.S. interests. The report Friday cites unnamed former law enforcement officials and others familiar with the investigation.

“This is yet more evidence that FBI leaders actually had no real evidence against the Trump team,” Nunes, a member of the House Intelligence Committee, told the Washington Examiner‘s Byron York. “Instead, they were simply trying to undermine a president they didn’t like and avenge Comey’s firing.”

“By relying on the Steele dossier—a fraudulent document funded by Democrats and based on Russian sources—FBI leaders were either complicit or too oblivious to notice they were being used in a disinformation campaign,” he added.

The inquiry forced counterintelligence investigators to evaluate whether President Trump was a potential threat to national security, and they also sought to determine whether the president was deliberately working for Russia or had unintentionally been influenced by Moscow.

FBI agents and several top officials became suspicious of then-candidate Trump’s ties to Russia during the 2016 presidential campaign but didn’t launch an investigation at that time because they weren’t sure how to approach such a sensitive and important probe, according to the Times‘ sources. However, President Trump’s behavior in the days surrounding Comey’s May 2017 firing, specifically two instances in which he seemed to tie Comey’s ousting to the Russia investigation, helped trigger the counterintelligence part of the investigation, according to the newspaper.

Responding to the report, President Trump said Saturday morning that the FBI launched the probe for “no reason & with no proof” aftehis firing Comey, whom he referred to as a “total sleaze.”

The Times says it is unclear whether Special Counsel Robert Mueller is still pursuing the counterintelligence angle.

Rudy Giuliani, President Trump’s lawyer, told the Times that he had no knowledge of the inquiry but said that since it was opened a year and a half ago and they hadn’t heard anything, apparently “they found nothing.” President Trump has also repeatedly and vociferously denied collusion with the Russians.

The Associated Press contributed to this report.