The UK's first youth police and crime commissioner, Paris Brown, has resigned from her post following criticism of messages she posted on Twitter.
The 17-year-old said she was quitting in the interests of everyone concerned, in particular the young people of Kent.
Police are investigating her over tweets she posted between the ages of 14 and 16 which could be considered racist and anti-gay.
Kent PCC Ann Barnes said it was "a very sad day".
Miss Brown was appointed last week to the £15,000-a-year post six days ago by Ms Barnes, who had said she would stand by her.
In a statement, the teenager, from Sheerness, said: "I accept that I have made comments on social networking sites which have offended many people and I am really, truly sorry for any offence that has been caused.
"I strongly reiterate that I'm not a racist and I'm not a homophobic [sic]."
She added: "I have fallen into the trap of behaving with bravado on social networking sites. I hope that this stands as a learning experience for many other young people."
"I now feel that in the interests of everybody concerned, in particular the young people of Kent who I feel benefit enormously from the role of a youth commissioner, that I should stand down," she said.
Ms Barnes said Miss Brown's tweets were not vetted before she was appointed but she was an "enthusiastic young woman with exceptional skills" who had performed well in a "very tough" interview process.
She said Kent Police's vetting procedures, which were used during the recruitment process, did not normally require social networks to be scrutinised for posts of this grade.
Miss Brown had been asked at the end of her job interview if there were any views she held, or if there was anything in her past that could embarrass her or the youth PCC post, and the teenager's answer had been "no", Ms Barnes added.
She said: "I'm sure many people today would not have the jobs they are in if their thoughts in their teenage years were scrutinised."
She said the events of the past few days had strengthened her desire to create the youth PCC post and she had no plans to resign.
She said Miss Brown would not receive any payment and the youth PCC role would be re-advertised in the summer.
The teenager was appointed last Wednesday to build a bridge between young people and policing in what was described as a "real hands-on role".
But The Mail on Sunday reported at the weekend Miss Brown had boasted about her sex life, drug-taking and drinking on her Twitter account @vilulabelle and had also posted violent, racist and anti-gay comments. The Twitter page has since been removed.
On Monday, two of Kent's Conservative MPs - Laura Sandys and Damian Collins - said the teenager should step down.
Labour's home affairs select committee chairman Keith Vaz also said he believed her views were "incompatible with holding office".
It later emerged Miss Brown's tweets were being investigated by Kent Police for possible criminal offences after the force received complaints.