Sen. Chuck Schumer REUTERS/Yuri Gripas

President-elect Donald Trump is drawing criticism from lawmakers after he questioned the legitimacy of US intelligence officials' findings on Russia's cyberattacks.

Senate Minority Leader Chuck Schumer cautioned Trump against mocking the nation's top spy agencies during an interview with MSNBC's Rachel Maddow:

“Let me tell you, you take on the intelligence community, they have six ways from Sunday at getting back at you,” Schumer said.

“So even for a practical supposedly hard-nosed businessman, he’s being really dumb to do this,” Schumer said.

Sen. Mark Warner of Virginia also expressed concerned about Trump's casting doubt on the work of the intelligence community.

"Really wish we saw more PEOTUS respect for our intelligence professionals," Warner said on Twitter. "Proves the need for Congress to give the American people a timely bipartisan probe."

In a Tuesday night tweet, Trump claimed his briefing on Russian cyberattacks was delayed until Friday and suggested intelligence leaders may have been trying to bolster their arguments.

"The 'Intelligence' briefing on so-called 'Russian hacking' was delayed until Friday, perhaps more time needed to build a case. Very strange!" Trump said on Twitter.

A senior US intelligence official immediately refuted Trump’s claim, saying the briefing with the heads of the NSA, CIA, DNI and the FBI was "always" scheduled for Friday, NBC News reported.

Since US officials determined Russia's involvement in the hacks of Democratic Party organizations in an attempt to help Trump win the election, the president-elect has remained skeptical of their conclusions.

"These are the same people that said Saddam Hussein had weapons of mass destruction," Trump's transition team said in a statement about the CIA's finding's last month.