Jack, who won Love Island last year with girlfriend Dani Dyer, has described the incident as a "lapse in judgment" and "not something that I’ll ever do again."
“I’ve made a mistake and I’m sorry for it and that’s the truth," he said in a newspaper interview.
According to The Sun newspaper, Jack went on a "blowout" last weekend with friends. After drinking on their night out, the group went to a hotel where Jack says he took the drugs.
There is no suggestion anyone else with Jack at the time had knowledge or supported the drug use.
Jack apologised for the "stupid mistake" which he linked to living in a 'new world' following his exit from the Love Island villa.
"I’m in a new world of partying and stuff, and being in circles that I would never normally have been in," Jack told the tabloid. “I’d never normally be in these situations but, yes, since winning the show I have been offered cocaine a lot.
“But I went out all night, I was drinking and I just got carried away and made a stupid, stupid mistake which I wish I’d never done, you know. I regret it.”
Jack revealed he had spoken to Dani about what happened.
“She doesn’t like all that. But obviously she’ll always support me. She said, ‘I’ll always support you, you made a mistake, we all make mistakes, but don’t ever do it again’," he said.
Jack concluded: “I’d say I’ve made a mistake and now I’ve got to deal with it. That was my mistake, but don’t do it. Nothing good ever comes from it.”
Following his victory with Dani on Love Island, Jack has launched a successful TV career.
He and Dani recently enjoyed their own ITVBe reality series and hosted red carpet coverage at the National TV Awards. He's currently readying to take part in ITV series The Real Full Monty, which will see Jack strip off to raise money for charity.