Former Treasury Secretary Larry Summers joined the chorus of voices calling on Washington to forge a solution to the massive tax hikes and spending cuts that loom early next year, saying it would be "an act of huge irresponsibility" for policymakers to sit on their hands.
Concerns are mounting that the political stalemate ahead of the presidential election next month will push the U.S. economy over the "fiscal cliff" after Jan. 1.
With both Democrats and Republicans focused on Election Day — less than three weeks away — Summers expressed worries that there appears to be no consensus in sight. (Read More: Alarm on Wall Street Grows as 'Fiscal Cliff' Nears .)
"We could take a situation, which is an economy that's starting to turn, that's got the prospects of a real recovery, and blow it if we go over that fiscal cliff, " Summers said Wednesday on CNBC's "Squawk Box."
"If we let everything rip, it would be an act of huge irresponsibility that would make a return to recession very likely, " said Summer, who was Treasury secretary in the Clinton administration and served as President Barack Obama's top economic adviser. "It would be a huge mistake."
The Harvard professor said there was an outside chance that both parties could come together, if the circumstances proved dire enough.
"I've been watching Washington for a long time, and one of the things you learn is that sometimes when the need is sufficiently great, the transition from inconceivable to inevitable can actually be fairly quick, " Summers said. He endorsed a balanced approach that would involve both higher taxes and spending cuts.
However, Summers took aim at the tax proposals offered by Romney, echoing criticism that the GOP nominee's plans lack detail. (Read More: Obama, Romney Tax Plans: A Real Case of 'Go Figure.' )
"How is Governor Romney going to cut taxes by 20 percent on all taxpayers like he promised, spend $2 trillion more on defense, and carry through on the higher income tax cuts that President Bush talked about?" Summers asked. "Where is that $8 trillion going to come from without blowing up the deficit or hammering the middle class?"