President Donald Trump's former chief economist warned that a coronavirus-driven global recession is a virtual certainty and that April may rank among the labor market's worst months for job growth on record.

On net, the government's official jobs report could tally as many as 1 million jobs lost in April as hiring grinds to a halt amid the coronavirus pandemic, according to Kevin Hassett, former chairman of the White House Council of Economic Advisors and current vice president and managing director of the Lindsey Group.

Even in the depths of the Great Recession, the U.S. labor market didn't lose 1 million jobs in a single month. Such a figure would be unprecedented in post-World War II America.

"We think the jobs number in early April might be as much as minus-1 million, or so," he said during an interview on CNN . "And if that happens, you're looking at one of the biggest negative jobs numbers we've ever seen."

Hassett explained that monthly employment reports are essentially the net sum of "millions and millions of people who are hired and fired every month." He predicted firing would largely stay the same but that "there will basically be no hires" as businesses across the country adhere to remote working guidelines and brace for a period of sharply reduced demand while Americans self-isolate.

"There's a whole bunch of really bad numbers coming in. And I think that's why the market is responding the way it is right now to the Federal Reserve's action," he said, referencing the Fed's decision to lower interest rates to near-zero levels and launch $700 billion of asset purchases. "I think the market understands that the Fed with its hundreds of economists has really started to think about the numbers coming in and is really sure that they're going to be terrible."

And even Hassett's assumption that firing behavior will remain constant could prove overly optimistic, as a string of layoffs appear to be coming down the pike as travel, retail, hospitality and industries reliant on foot traffic predict massive losses.

Hassett noted the U.S. isn't technically destined to fall into recession as a result of the coronavirus, since recessions are defined as two consecutive quarters of contraction in gross domestic product, and right now the only real certainty is that the second quarter is going to be "very terrible."

"If you're going to have a recession, you have to have two bad quarters. I think that's going to depend on whether we get ahead of the curve on the coronavirus. And I think that's a big unknown right now," he said.

He believes the odds of a global recession, though, "are close to 100% right now" and that U.S. growth is likely to contract 5% in the second quarter of the year. Economists widely predict economic weakness in China, Europe and around the world will drag on U.S. producers and domestic economic output.

The White House has waved off concern about a pending recession, with Treasury Secretary Steven Mnuchin and National Economic Council Director Larry Kudlow insinuating the stock market's sell-off represents a buying opportunity for investors. A market-halting circuit-breaker designed to prevent steep losses on Wall Street has been triggered three times in the past week. The Dow Jones Industrial Average was down as much as 12% in midday trading Monday.

But Hassett is not the first former Trump administration official to sound alarms about the state of the economy.

Gary Cohn, Trump's former National Economic Council director, told " Anderson Cooper 360 " last week that he is "willing to say we are in a recession right now."