Some Democrats saw abundant irony in Trump blaming Obama for indecisiveness against a Russian operation that Trump himself has long seemed to play down.
In a flurry of weekend tweets and a prerecorded television appearance, Trump said his predecessor failed to act after the CIA informed him in August that Russian President Vladimir Putin had personally ordered an operation to help Trump defeat Hillary Clinton in the November election.
"Since the Obama Administration was told way before the 2016 Election that the Russians were meddling, why no action?" he asked in one tweet.
In another, alluding to a Washington Post article that laid out the Russia timeline, he tweeted: "Obama Administration official said they 'choked' when it came to acting on Russian meddling of election. They didn't want to hurt Hillary?"
A top Trump aide, Kellyanne Conway, was more blunt still.
"It's the Obama administration responsible for doing absolutely nothing from August to January with the knowledge that Russia was hacking into our election. They did nothing. They're responsible," she said Sunday on ABC.
Some Democrats saw abundant irony in Trump blaming Obama for indecisiveness against a Russian operation that Trump himself has long seemed to play down -- including when he fired FBI chief James Comey for pursuing his investigation of "this Russia thing."
But one influential Democratic lawmaker joined in the criticism of the previous president.
Adam Schiff, the ranking Democrat on the House Intelligence Committee, said on CNN that he understood that the Obama administration was worried about being seen as "trying to tip the scales for Hillary Clinton."
But he went on: "The American people needed to know. I didn't think it was enough to tell them after the election... I think the administration needed to call out Russia earlier, needed to act to deter and punish Russia earlier and that was a very serious mistake."
Another Democrat, Senator Ron Wyden, a member of the intelligence committee, expressed similar disappointment.
"I am troubled learning this new information that the Obama administration didn't do more," he told CNN on Friday. Such matters should transcend politics, he added.
The Washington Post, in a behind-the-scenes account of the Obama response to reports of Russian meddling, said that amid confidence that Clinton would win and for fear of Obama being seen as interfering, the administration warned Moscow but left countermeasures for later.
The Post said Obama issued four warnings to the Russians -- including one he delivered directly to Putin -- causing Moscow to pull back on possible plans to sabotage US voting operations.
But after Trump's shock victory in November, some Obama administration officials expressed regret at the lack of tougher action.
"Wow, did we mishandle this," a former administration official told the newspaper.
In an interview with Sunday's "Fox and Friends" program, Trump groused about Obama's response, saying: "If he had the information, why didn't he do something about it? He should have done something about it. But you don't read that. It's quite sad."
Following Trump's election win, Obama expelled 35 Russian diplomats and added new sanctions.
While Schiff criticized Obama, Senate Democratic leader Chuck Schumer pushed back hard.
The New York lawmaker helped steer a bill through the Senate this month to toughen sanctions against Russia and bar Trump from weakening them on his own.
The bill passed with overwhelming bipartisan support, but Trump administration officials have been working to weaken the House version.
"If Donald Trump wants to do something about Russia and Russia meddling, instead of saying Obama didn't do enough, support our sanctions bill," Schumer said on ABC.
Criticism of Trump's failure to sharply condemn Russian interference has continued to vex his administration.
As recently as Tuesday, White House spokesman Sean Spicer could not give a clear answer when asked repeatedly whether Trump believes the Russians interfered in the 2016 elections.
"I have not sat down and talked to him about that specific thing," Spicer said. "Obviously we've been dealing with a lot of other issues."