The parents of teenager Megan Meier have expressed anger at the news that the adult whom they claim bullied their daughter into suicide will not be prosecuted.

Meier, who was 13, struck up an online relationship with a 'teenager' known as 'Josh' via MySpace, but 'Josh' was in fact the mother of a former friend of Meier's.

'Josh' broke off the online relationship after six weeks and began abusing Meier and posting unpleasant messages. Meier, who suffered from depression, hanged herself the next day.

Her parents went public with the case after local law enforcers told them that there was nothing they could do.

Meier's home town of Dardenne Prairie has since passed a law making online harassment a misdemeanour with a maximum penalty of 90 days in jail and/or a $500 fine.

"Our daughter committed suicide," Meier's mother said. "I still feel what [the adult] did is absolutely criminal."

Jack Banas, prosecuting attorney for St. Charles County, said that there was nothing he could do.

He explained that there was no way of making a positive identification of who had sent the messages, and that the majority of the content was inoffensive.

"People are upset that a parent got involved in something so childish, and that a young girl committed suicide," he said.

"There are a few statements at the end that are a heated argument. That is why you have a hard time making a harassment case."

Banas added that current statutes allow action only when an individual sought to frighten, disturb or harass.