No further action is to be taken against Paris Brown, formerly Britain's first youth crime commissioner, Kent Police have said.
The 17-year-old had been accused of racism and homophobia after making comments about gay people and others on Twitter when she was between 14 and 16.
Miss Brown became Britain's first Police and Crime Youth Commissioner after being awarded the £15,000-a-year job by Kent's Police and Crime Commissioner Ann Barnes.
On April 9, only a few days after being appointed to the role, she was forced to resign when details of her earlier tweets emerged after an expose by the Mail on Sunday.
A spokeswoman for Kent Police said today: "We have spoken to the CPS about our findings, and given them our view that this case does not pass the evidential threshold for prosecution.
"We will make no recommendations to them for charges and will take no further police action having discharged our duty to investigate."
"Whilst some of the language used is offensive, particularly the comments which derogatorily refer to particular social groups, we do not believe that in the context they are grossly offensive on a reasonable objective assessment considering intent."
Miss Brown was said to have been "pleased" with the decision.
A statement, the from Olswang, the law firm representing her, said: ""Paris and her family are pleased this matter has been brought to a close. She has had a difficult time recently, in part due to the media and inappropriate police scrutiny.
"She is glad to put this behind her and move on."
Miss Brown, from Sheerness in Kent, was forced to issue a grovelling apology for the offence she caused.
She denied being anti-gay or racist, and said she is against taking drugs, insisting that a reference on Twitter to making "hash brownies" was from a Scooby Doo film. The offensive tweets have now been deleted.
In tears as she made her statement, she told reporters: "I have fallen into the trap of behaving with bravado on social networking sites. I hope this may stand as a learning experience for many other young people."
Miss Brown was taken on by police to provide a young person's perspective on policing and to help prevent crime.
The teenager's Twitter account was not checked as part of the recruitment process.
On Saturday it emerged lawyers representing Miss Brown had written to the chief constable of Kent Police complaining of a "wholly disproportionate" response to the Twitter comments.
Her questioning by officers came after the force received more than 50 complaints from members of the public.
Her lawyers, Olswang, wrote to Chief Constable Ian Learmonth about the scope and nature of the investigation, including the decision to seize her phone and for Special Branch to quiz her.
As part of the investigation, Miss Brown was requested to attend an interview under caution on April 14.
In their letter, her lawyers said: "As we are sure that you will readily understand, being subject to a police investigation is highly distressing for any person, but especially so for a teenager, particularly one who has been recently subject to such adverse media coverage.
"In such circumstances, we believe that the police must weigh carefully the extent to which an investigation relating solely to social media activity is merited."
Olswang also referred to the interim guidelines from the Director of Public Prosecutions (DPP), Keir Starmer, regarding prosecutions relating to social media.
Another youth commissioner will be appointed later this year, but Mrs Barnes said there were "lessons to be learned" before that happens.