Paris Brown, 17, yesterday resigned after appearing to use homophobic, racist and violent language in tweets posted before she took the job with Kent Police. Kent Police and Crime Commissioner Ann Barnes appointed Brown last week to the £15,000 a year post.
Barnes, who had said she would stand by Brown, 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.
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", Barnes added.
Chris Fisher, employment partner at international law firm, Mayer Brown, said: "Where social media sites are used, care needs to be taken."
Not every employer uses social media sites as part of their vetting process, he said. Some companies "do this as a matter of course" but others do not want their recruitment decisions "influenced by information" that is not relevant to a person's ability to do a job.
"One of the biggest risks is discrimination. Sites will often contain personal details, which could form the basis of protection against discrimination under the Equality Act 2010, such as age, religion or belief, sexual orientation or marriage status for example.
"Therefore, if an employer has access to this information and then uses such information as the basis for refusing to recruit or to dismiss that person, then the employer's action could constitute unlawful direct discrimination."
Fisher continued: "Vetting job applicants using information contained on social media sites could also have implications for employers under the Data Protection Act.
"While employers could use that information, the Employment Practices Data Protection Code recommends employers give job applicants the opportunity to comment on the accuracy of any background checks or information it has obtained about them.
"So employers should notify applicants at the start of any application process that a vetting exercise using social media sites forms part of the process."
Brown's tweets are also being investigated by Kent Police for possible criminal offences after the force received several complaints. In one she wrote: "I'm either really fun, friendly and inclusive when I'm drunk or I'm an anti social, racist, sexist, embarrassing a*******, often it's the latter."
In a statement released last night, Brown said: "I have made this decision after a great deal of thought and consultation with my family.
"As I made clear over the weekend, I accept that I have made comments on social networking sites which have offended many people. I am really sorry for any offence caused.
"I strongly reiterate that I am not racist or homophobic. 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."
She added that she felt the "recent media furore" would continue to hamper her ability to perform the job to the level required.