The pop star was the subject of an undercover media operation carried out by Mazher Mahmood, also known as the "Fake Sheikh", for The Sun on Sunday.
She was arrested in June 2013 under suspicion of supplying class A drugs to the journalist and has spent the past year awaiting trial.
Jones, the co-founder of PR agency Hackford Jones, and Contostavlos had to remain silent on the issue until the trial collapsed last Monday when the judge decided Mahmood had lied to the court.
Jones (left) said he has been working as Contostavlos’ PR manager "since the very beginning" when she was still a member of hip-hop group N-Dubz and described their relationship as "very close".
He said it was "frustrating" not to be able to tell Contostavlos’ version of events and challenging as a PR.
"I’ve never experienced a client not being able to talk to the media," he said. "All I could do was advise Tulisa to keep her head down and tell the press we can’t talk, even off record."
Jones admitted he was unsure what the repercussions would be to her image. Last Friday (25 July), Contostavlos was again in court and was this time convicted of assaulting celebrity blogger, Savvas Morgan. Jones said Contostavlos' camp was "extremely disappointed" with the ruling and would appeal against it.
He claimed it was difficult to tell how damaged her reputation was because she had not been working for a year: "It’s quite difficult to work out what damage a particular action has caused because you’ve got nothing to benchmark it."
However, he believed the drugs court case had a positive outcome in that everyone now knew what happened. "When it’s a front-page headline involving cocaine, people don’t read the details – they just see a high profile celebrity," he said.
He said that Contostavlos was already back in the studio and a BBC Three documentary on her journey through the court case will air tonight (28 July).
Despite reports that the singer considered suicide during the 13 months she was battling the court case, Jones said: "What she’s talking about in the interviews is that it’s given her renewed vigour to release music.
"I think one good thing that comes out of this case is that people have put the spotlight on the practices of undercover journalists; some of the stuff that went on during this case is really horrific and should not be allowed," he added.
Throughout the case, Mahmood had argued that he was acting in the public interest.
Jones disagreed, arguing that Contostavlos did not deserve the negative attention. He argued she was an easy target as an X Factor judge and the newspaper made her life a "living hell" over the past year.
"There is a lot of argument about who in the UK does deserve that but I don’t believe that a celebrity is the right target for this kind of journalism," he said.
Jones explained that despite everything, he did not hold a grudge against the newspaper that initially made the allegations: "The relationship has been helped by a change in team.
"I wouldn’t be getting very far if I said I wouldn’t work with The Sun – while you’re battling it out in court one minute and then talking with them about a Little Mix story the next, it would be difficult."