Staten Island District Attorney Michael McMahon went on a six-figure spending spree after taking over in January, forking over $50,000 for new carpeting and furniture and another $67,000 for an SUV, The Post has learned.

The Democratic prosecutor claims the expenditures were necessary because his Republican predecessor, Dan Donovan, left the office in shambles and handed over a vehicle with mechanical problems that had 120,000 miles on it.

McMahon spokeswoman Ashleigh Owens defended the purchase of a GMC Yukon, saying that the seven-seater is used to transport staff to events and that “similar models are driven by all DAs and city officials.”

Asked about the $10,000 for carpeting and the $40,000 in new furniture, according to insiders, Owens again blamed Donovan. She said that when he packed up last May after being elected to Congress, Donovan left the DA’s executive office locked and untouched for months, with the air conditioner blasting — resulting in an equipment malfunction, which then led to flooding and mold.

She also said that McMahon remodeled the executive suite to create a new conference room and that the furniture was ordered to “fill that newly created space.”

“Other miscellaneous pieces of furniture have been ordered as standard upkeep for broken pieces throughout the office,” Owens added. “These expenditures are modest and for office upkeep, especially when you consider the Donovan administration spent $145,000 in 2014 for carpet alone.”

Donovan declined to comment, but his allies pointed out that Daniel Master served the final seven months of Donovan’s term, so the DA’s executive office never went unattended. They also said McMahon repainted his executive office twice before settling on “Congressional Blue.”

Two sources said further that the $145,000 Donovan spent on carpeting two years ago was for all the offices in his complex, not just his.