Lyft is spending big again in New York City to beat back Uber.

The ride-hailing app is slashing fares for passengers by 50 percent for all hours between Monday and Friday — and is letting drivers keep 100 percent of the tab.

The exceptionally sweet deals are being offered for a “limited time” and “could last several weeks,” Vipul Patel, Lyft’s general manager for New York City, told The Post.

The discounts are stepped-up versions of what Lyft has offered in the past as it spends heavily — to the tune of $50 million a month nationwide, according to sources — to gain market share against its bigger rival. A Lyft spokeswoman said the new incentives fall “well within” the startup’s existing budget.

“When we bring people on board, they tend to stick around,” Patel said, adding that Lyft’s New York business has surged tenfold over the past 12 months.

Still, Uber’s Big Apple business is more than seven times as large as Lyft’s, according to Slice Intelligence.

Lyft has offered zero-commission driver deals since January, but has required drivers — whom Lyft usually charges a cut of 20 to 25 percent — to rack up 75 rides in a week to win them.

“It’s been a really successful program,” Patel said. “We thought we’d give all drivers a taste of that.”

Eyeing summer hotspots, Lyft also said it’s launching in the Hamptons, Cape Cod and the Jersey Shore in the coming weeks.