Chris Christie made his “ultimate mistake” with Donald Trump when he bragged about talking to President Obama on election night and offered to let Trump — an infamous germaphobe — use Christie’s cellphone to talk to Obama.

“If you win, he’s going to call my phone, and I’ll pass it over to you,” Christie said, according to excerpts of a new book obtained by the Daily Mail.

A visibly angry Trump snapped at his top campaign aide.

“Hey Chris, you know my f–king phone number. Just give it to the president. I don’t want your f–king phone,” Trump fumed.

Christie, who never received a role in the White House despite his steadfast support for the president, “wouldn’t recover” from the phone debacle, the report said.

Christie made yet another critical mistake when he “pushed himself” into photos with Trump on election night.

Trump’s son-in-law Jared Kushner — whose father was prosecuted by Christie, then a US attorney in New Jersey — gave the Garden State governor the ax right after Trump’s victory.